JOHN YANG: Tonight on PBS News Weekend.

As a U.S.-China trade war brews, China urges the Trump administration to abolish reciprocal tariffs and correct its mistakes.

Then, we look at how a social media app became a hub for hate crime and radical extremists.

And 113 years since the sinking of the Titanic, we get a new digital look at the world's most famous shipwreck.

MAN: To see it all like this, well lit up in context, you can see off into the distance.

That's a view that you never have at the wreck site.

(BREAK) JOHN YANG: Good evening.

I'm John Yang.

The developing trade war between the United States and China keeps ratcheting up.

There are reports tonight that China has suspended exports of rare earth minerals critical to automakers, semiconductor companies and military contractors.

And Commerce Secretary Howard Lutnick said today that the electronics the administration exempted from reciprocal tariffs on Friday could be subject to different levies in the future.

Earlier, I spoke with Katrina Northrop, China correspondent for the Washington Post.

I asked her about the Chinese reaction to the initial exemption of those electronics.

KATRINA NORTHROP, CHINA CORRESPONDENT, THE WASHINGTON POST: They said that it was a good step.

They're still criticizing the tariffs, but it does show a window of opportunity potentially for the two sides to talk.

There's still a lot of problems and a lot of kind of barriers to get them together.

But that exemption, I think, is going to be seen positively in Beijing.

JOHN YANG: What do the economists and analysts say about the effect on the Chinese economy of a trade war?

KATRINA NORTHROP: It's huge.

The Chinese economy is not doing well.

It's struggled to rebound from the pandemic.

They've had a property sector crisis.

They've had high youth unemployment.

So they started at a bad baseline.

And exports have been a really bright spot in the otherwise sluggish economy.

JOHN YANG: Katrina, you're in Taipei.

Like most Western journalists because of the restrictions that the -- that Beijing has put on Western journalists.

Is it possible to tell, though, how this is affecting or the reaction of the Chinese people to this?

KATRINA NORTHROP: It's hard to tell, but there's a lot of concern, like there is in the U.S. around a spiraling trade war.

There are many supply chains built up in China around serving the American market.

JOHN YANG: You talk about China sort of looking or interested in a deal, but outwardly they've been very defiant.

Help us understand the Chinese reaction and response to all of this.

KATRINA NORTHROP: Yeah, they've stood very firm.

The people that we talk to say that they don't want to be seen as weak.

They don't want to be seen as being pressured by Trump.

And Trump seems to be waiting for Xi Jinping to call him, and Xi Jinping doesn't seem willing to make that call.

So we're waiting to see what happens or whether we continue to escalate.

I don't think that's out of the question.

Think we could see more escalation before we see any type of negotiation.

JOHN YANG: And is China prepared for that escalation?

Do they have plans in their back pocket, as it were?

KATRINA NORTHROP: Yeah, China has been preparing for a trade war with the U.S. since the first trade war with the U.S. in the first Trump term.

And there's been a huge push to kind of create a more independent economy.

At the same time, they've also developed this whole suite of tools to push back against Washington.

So it's not only tariffs that they have in their pocket.

They have export controls, which they've increasingly used.

They have sanctions.

They can go after specific U.S. Companies.

On Friday, Beijing said that they would not increase tariffs further from the 125 percent that they are on right now.

But that doesn't mean that they won't use these other tools like export controls to go after Washington.

JOHN YANG: What's this doing to the overall relationship between these two countries?

KATRINA NORTHROP: Yeah, I think there's a lot of concern around this escalating beyond just a trade war.

This could very easily move into a broader spiraling tension over things like Taiwan or South China Sea or other issues.

And so economic and trade ties have long been a stabilizing force in the relationship.

It's brought the two countries together, it's forced them to talk.

And right now, we're closer to economic decoupling than we ever have been.

And many people are concerned that the two leaders won't be able to get the relationship back on the right track.

JOHN YANG: Katrina Northrop of the Washington Post.

Thank you very much.

KATRINA NORTHROP: Thank you for having me.

JOHN YANG: In tonight's other news, two Russian missiles struck the eastern Ukrainian city of Sumy as people there gathered to celebrate Palm Sunday.

Ukrainian officials say at least 34 people were killed and more than 100 injured.

The attacks appear to be part of the Russian spring offensive that Ukraine warned about last month.

On Friday, special envoy Steve Witkoff was in Russia to encourage President Vladimir Putin to accept a truce as President Trump's patience wears thin.

DONALD TRUMP, U.S. President: I think Ukraine, Russia might be going okay, and you're going to be finding out pretty soon.

You know, there's a point at which you just have to either put up or shut up or see what happens, but I think it's going fine.

JOHN YANG: Ukrainian President Volodymyr Zelenskyy's chief of staff says the missiles that hit Sumy were armed with cluster munitions to cause as much damage as possible.

Pennsylvania Governor Josh Shapiro and his family are safe tonight after police say an arsonist attacked his official residence.

Shapiro said Pennsylvania State Police alerted him and his family to the fire and safely evacuated them.

Fire crews quickly put out the flames, but a significant portion of the residence is damaged.

An investigation is underway.

The man the Trump administration acknowledges it deported by mistake is alive and secure.

That's according to the first court ordered daily report on the status of Kilmar Abrego Garcia that the administration submitted on Saturday.

In the court filing, a State Department official said Abrego Garcia is being detained by the Salvadoran government.

The report didn't say anything about what the administration is doing to facilitate his return to the United States.

Information, a U.S. district court judge said, had to be updated daily as Abrego Garcia's case continues.

President Trump is to meet with the president of El Salvador tomorrow at the White House.

The White House position says President Trump is in excellent health and fully fit to serve as commander in chief.

The White House released the results of Mr. Trump's annual physical conducted Friday at Walter Reed Medical Center.

The report says Mr. Trump has a scar on his right ear from last year's assassination attempt, is taking two medications to control his cholesterol and is current on all recommended vaccinations.

The report also notes that his active lifestyle includes frequent victories in golf events.

Still to come on PBS News Weekend, the online hub for hate crime and radical extremists, and we bring you a groundbreaking new look at the Titanic.

(BREAK) JOHN YANG: Proponents of social media say that it bridges physical distance to build communities of like-minded people.

But what binds them together can sometimes be hatred and violence.

A joint investigation by ProPublica and PBS FRONTLINE details the shadowy world of online hate networks.

Their investigation focuses on the platform Telegram, and it's detailed in a new documentary, "The Rise and Fall of Terrorgram."

A.C. THOMPSON, Investigative Reporter, ProPublica: At first it's just a handful of chat rooms and channels on Telegram.

Then it is bigger and bigger, and finally it takes on a formal shape, and people within that group say, now we're starting something called the Terragram Collective, and this is going to be our organized arm that is going to generate in depth propaganda, in depth material for this community.

JOHN YANG: The investigation identified 35 crimes linked to Terrorgram, including bomb plots, stabbings, and shootings.

A.C. Thompson, who you just saw there, is one of the reporters who worked on the project.

He covers hate crimes and racial extremism for ProPublica and PBS Frontline.

A.C. for people who aren't familiar with Telegram, what is it about this platform that makes it so attractive to the people who form Terrorgram?

A.C. THOMPSON: Terrrogram is a massive, massive platform.

About a billion people use it, most of them outside of the US.

What was appealing to various types of extremists about Telegram was the fact that there was very little moderation on it.

So for a very long time, extremists of all different types, including the Terror Graham community, which was a white supremacist neo Nazi terror group, were able to use this platform to basically commit crimes.

JOHN YANG: One of the cases you look at in the documentary is the case of Yuri Krajczyk.

He's a teenager who carried out a shooting outside of a LGBTQ bar in Bratislava, Slovakia.

And you looked at his ties to Telegram, his ties to various people on Telegram.

Let's take a look at that.

PIERRE VAUX, Open source investigator: You're looking for what nodes turn up in networks over and over again.

So Krychick's account is Bob Bowie, and we can expand that one.

He was a very active user on these channels.

I've got another 40 channels he was in.

A.C. THOMPSON: Holy.

These are all chats?

PIRRE VAUX: Yep.

A.C. THOMPSON: Oh, wow.

JOHN YANG: What does his case tell us about these online hate networks?

A.C. THOMPSON: He's emblematic of the problems that we see here.

So he gets into the Telegram community when he's 16 years old, and over the span of three years, he is encouraged and groomed and pushed to engage in white supremacist terrorism.

And then finally, in 2022, he goes out and does it, and he attacks an LGBTQ bar.

He shoots three people and kills two, and the community that he'd been interacting with celebrates him as a hero and a saint and someone to emulate.

Your documentary includes a statement from Telegram, they told you that calls for violence from any group were not tolerated on our platform.

That said, why was the Terrorgram Collective allowed to sort of be there for so long?

A.C. THOMPSON: Yeah, that's a thing that was pretty disturbing to us.

You know, we can trace the early days of terrogram to 2019, and it starts with a couple of accounts, and it grows into this big community with hundreds of accounts and thousands of followers over about a five year span.

And in that time period, we didn't see real sustained efforts by Telegram to push these people off of the platform.

JOHN YANG: The defenders of these sites and the participants in these sites say they're merely using free speech, expressing free speech.

What do you make of that?

A.C. THOMPSON: The people that we're looking at in the telegram scene are not just saying, I'm racist, I'm antisemitic, I'm anti-LGBTQ.

What they were doing for five years, half a decade, was encouraging people to commit terrorist attacks.

So when went on to Telegram and investigated these spaces, we would find bomb making manuals, we would find poison recipes, we would find hacking tools, we would find hit lists.

It's just the sort of stuff that doesn't fall really into the free speech space, but falls into the terrorist material space.

This is about terrorism.

JOHN YANG: You mentioned earlier the sort of transient nature of these groups on these sites.

They move from one site to another.

What does that tell you about online hate groups?

A.C. THOMPSON: Over the last 10 years, I've been watching these groups and these actors move from one platform to the next.

And as they get bumped from one place because of hate speech, because of moderation, because maybe they're posting bomb materials, they go on to the next one.

And I think overall, the social media providers have not had a unified sort of strategy for dealing with this.

JOHN YANG: And from your reporting, what could deal with this?

Is it law enforcement?

Is it regulation?

A.C. THOMPSON: There's two pieces here.

I think what you really are looking at is good corporate behavior from the social media platforms, not allowing people to run a terrorist network on their site for years.

And they're just for a very long time, Telegram didn't seem to be responding to that kind of concern about criminal activity.

Now it has stepped up it's moderation.

It is policing the platform much more strongly these days than it did.

But it was a real wild thing to see that sort of material just circulating across a very large platform.

JOHN YANG: A.C. Thompson of ProPublica and PBS Frontline, thank you very much.

A.C. THOMPSON: Thank you.

JOHN YANG: More than 2 million Americans are living with limb loss.

A Government Accountability Office report says that number is expected to almost double by 2050.

Yet recent reporting by KFF Health News finds that many who've lost limbs are hitting roadblocks when they try to get insurance to cover the cost of prosthetic limbs.

Some companies even question whether these life changing devices are medically necessary.

Ali Rogin spoke with Michelle Andrews, a contributing writer for KFF Health News.

ALI ROGIN: Michelle, thank you so much for joining us.

Why are these denials happening and what do we know about the scale of the problem?

MICHELLE ANDREWS, Contributing Writer, KFF Health News: Well, I can't actually speak for the insurers, but I can say that when I've asked them about denials, they've said, well, we do in fact cover these prosthetics when they're medically necessary to replace a body part or use every day.

But when you talk to, you know, advocates, you find out that's not actually the case.

There are a couple million people who need prosthetics.

And so, you know, given that these are fairly expensive items, I think it's one of those things that, you know, may be on the chopping block when they're at ways to save money.

And, you know, these are for profit entities.

ALI ROGIN: That's a very good point.

Are we seeing this happen more with private insurance, Medicare or Medicaid, or is there really no distinction?

MICHELLE ANDREWS: There's a big difference.

Public insurance, Medicare, the VA, Medicaid to some degree, they're pretty good about covering prosthetics.

But in private insurance, you do see some good coverage, but it's all over the map from what I'm told.

And that can mean that it really isn't very good at all.

ALI ROGIN: We spoke to a number of people who either have had their request for coverage denied, some are still fighting.

Some have received their prosthetics, but only after an appeals process.

I want to play some of their stories.

LEAH KAPLAN, Spokane, Washington: I'm Leah Kaplan, and I'm from Spokane, Washington.

RANDI GLISSON, Charlotte, North Carolina: My name is Randy Glisson.

I am from Charlotte, North Carolina.

PETER MELLO, Whitman, Massachusetts: My name is Peter Mello.

I live in Whitman, Massachusetts.

LEAH KAPLAN: I've had three denial letters.

I feel a little defeated in a way, and I feel like it's.

I feel like I'm in the wrong for asking something that I need.

PETER MELLO: The access to them is met with red tape, brick walls, denials, delays.

RANDI GLISSON: I even got a letter saying that basically I don't do anything that requires two hands.

So I didn't.

I didn't need one.

LEAH KAPLAN: They've actually made my arm already and psionic.

They sent my hand in already and it's literally sitting two miles away from me at the office.

They just cannot give it to me because the insurance.

RANDI GLISSON: I've honestly kind of given up at this point.

And I know that sounds terrible, but it's just.

There's literally nothing else I can do.

LEAH KAPLAN: The insurance, they just keep on sending me a letter just over and over saying, this is a lux -- this is considered a luxury item.

You're kind of baffled by, like, how could you say that about something that you need?

PETER MELLO: You have to prove to these people that your life is worth it.

Get somebody on the phone who has your quality of life dangling in front of you like a carrot, and they're fighting you tooth and nail to get that quality of life.

It's demoralizing.

ALI ROGIN: You know, I think a lot of people hearing that would think, how could anybody say that, you know, a human being doesn't do anything that requires two hands.

It feels like a basic human right.

MICHELLE ANDREWS: It sure does.

And hearing those people talk about the roadblocks and the, you know, the hoops they've had to jump through is just -- it's really sad.

It is something that we all deserve to be able to have, you know, both hands if we want them, and legs and to be able to walk around.

It's not a luxury.

ALI ROGIN: And does it reflect stories that you've heard from other people?

MICHELLE ANDREWS: Absolutely.

People run into just so many, sometimes bizarre seeming roadblocks.

They might run into weird caps, you know, where we'll only cover one limb over the course of your lifetime or will only cover $50,000 one time.

They're told that they're not medically necessary or that they don't cover that particular technology.

When it's technology that's not especially, you know, experimental, it's a microprocessor knee that's been in use for 30 years and that really helps people on uneven surfaces.

It senses if you're going to fall, it actually is, you know, it's a safety device to have a good knee.

ALI ROGIN: Is there any effort taking place among policymakers, lawmakers to address what seems to be an uptick in denials?

MICHELLE ANDREWS: About half the states have laws on the books that require some sort of prosthetic coverage.

So those are called insurance fairness laws.

And then there are some that deal with recreational activities.

There's nothing at the federal level that's been passed that requires coverage of prosthetics.

There have been some efforts in that area, but so far that hasn't happened.

And I think it's important to point out that federal protection is critical because those state laws only protect you if you have health insurance with a plan that is regulated by the state.

And more than half of people are not in those kinds of plans.

They're in big employer plans that are federally regulated.

ALI ROGIN: Michelle Andrews, contributing writer for KFF Health News.

Thank you so much for joining us.

MICHELLE ANDREWS: Thank you for having me.

JOHN YANG: This week marks 113 years since the sinking of the Titanic.

A tragedy that's captivated generations.

It's been the inspiration for three big movies.

Now there's a new tool for exploring it.

A full scale digital twin of the wreckage created with cutting edge 3D scanning technology.

That's the subject of a new National Geographic documentary, "Titanic: The Digital Resurrection," which is streaming on Hulu and Disney Plus.

Earlier I spoke with Titanic analyst Parks Stevenson.

I asked him to compare the virtual experience with the real life visits to the wreckage in a submersible.

PARKS STEPHENSON, Titanic Analyst: In a submersible, your view to the outside world is like a 7-inch viewport.

And your light only carries less than 100 meters in front of you.

So you only see the wreck a little bit at a time.

To see it all like this, well lit up in context, you can see off into the distance that's a view that you never have at the wreck site.

JOHN YANG: Did anything surprise you about what you saw on the digital twin?

PARKS STEPHENSON: Everything I saw surprised me.

My experience has been through dives, through studying digital imagery captured by cameras.

I've seen the wreck in context, put together in the early days by artists who painted the wreck after they studied all of the imagery, but that's all involving human intervention.

This, however, is completely data driven.

And so now I'm seeing the wreck in its context for the first time.

JOHN YANG: What were some of the biggest questions that got answered with this new way of looking at it?

PARKS STEPHENSON: On the first render that was sent to me was of the stern.

I've always tried to explain why the stern section is in such worse condition than the bow section.

And in this first render, it was depicted so accurately that I could tell part of what we learned Tthat the stern spiraled down, the rudder dug in, and the whole stern section tweaked.

When it tweaked, all those connections, the decks and the frames and the shell plating, they were all stressed.

Some gave way immediately.

But as we've learned from experiments held by the wreck, anything that was tweaked, corrosion is accelerated.

And that's why she's now flattened in the middle, the stern section is.

That was just one glance, and to my engineer eye it's what I needed.

JOHN YANG: And you say there's some new questions that arose.

What are some of those?

PARKS STEPHENSON: People have questions about how long the Rhett's going to be with us.

And I've heard some of the more dire predictions about she's going to be gone in 20 years or so.

That's not true.

The wreck will be here long after you and I are gone, but it's not going to look like it does now.

There are some of the lighter structures that will erode or corrode within the next few years or so.

With every bit of corrosion, it may open up new possibilities to penetrate and look inside the wreck.

For instance, in the stern, I'm seeing potential new penetration points so where we can go inside the stern for the first time.

In n the bow, the skin of the ship, it's pulled away from the skeleton enough that we could probably now get inside of there.

So we may be able to get down into the interior boiler rooms, which we've never been able to get into before.

JOHN YANG: Beyond sort of answering these mysteries of history, are there lessons to be learned that could be used today, that could be important today?

PARKS STEPHENSON: The Titanic story was originally built off of a oral history.

All we had were the statements of the survivors.

And as I've interviewed participants in historical events over the years, I found that human memory is fallible.

So the narrative of Titanic, I think, is going to start changing as we get more and more stories out of the steel.

What I'm concentrating on right now is reverse engineering the breakup based on the evidence that we've documented on the ocean floor and find out exactly why she broke up.

The more I study the wreck and the pieces on the bottom, I'm finding more and more evidence that Titanic was actually well built, well designed, everything was done right, and yet look what happened.

That's the lesson from Titanic.

Don't assume that just because everything's going right, you've got everything figured out.

JOHN YANG: Parks Stephenson, thank you very much.

PARKS STEPHENSON: Thank you.

JOHN YANG: And that is PBS News Weekend for this Sunday.

I'm John Yang.

Thanks for joining us.

Have a good week.