NOEL KING, HOST:
The Trump campaign ran an ad on Facebook that features a symbol used by the Nazis. It's a big upside down red triangle that's associated with Nazi concentration camps. Facebook took the ad down, but the Trump campaign defends it, and NPR's Bobby Allyn is going to explain why.
BOBBY ALLYN, BYLINE: The ad plays on some familiar Trump themes, calling the mass street demonstrations mayhem, blaming riots on antifa despite providing no evidence to back that up. But under the words is a giant upside down red triangle. It's a symbol that was sewn into the uniforms of Nazi concentration camp prisoners. The ads were swiftly condemned by groups like the Anti-Defamation League, which tracks hate online. Jonathan Greenblatt is the league's CEO.
JONATHAN GREENBLATT: Nazi symbols are never OK. Hate has no place in our politics. There are plenty of other ways they can communicate their point.
ALLYN: The Trump campaign is knuckling down. They're defending the ads and criticizing Facebook for removing them. A Trump campaign spokesman says the triangle is also used as an emoji everyday texting conversations. And they point to obscure online merchandisers who sell a few items with the word antifa next to an inverted red triangle. Greenblatt says he's troubled that once the Trump campaign was reminded of the symbol's history, they continued to defend it.
GREENBLATT: So what's so alarming about this is that once it's been identified as a symbol associated with the Nazi regime, it shouldn't be a difficult call to take it down.
ALLYN: It took days for Facebook to say the advertisement violated their rules against hate. By that time, the various ads featuring the triangle had gathered more than a million impressions online.
SARAH ROBERTS: So in a way, it's kind of closing the barn door after all of the horses have gotten out of the barn.
ALLYN: Sarah Roberts is a professor at UCLA who studies content moderation. She says for the Trump campaign, it was a win regardless of what Facebook did in response.
ROBERTS: They get to circulate the ads for some period of time, and then they get to capitalize on a narrative that I believe to be demonstrably false that they are somehow censored or impeded from sharing their perspectives on social media.
ALLYN: Facebook has generally taken a hands-off approach to Trump's misleading or inflammatory posts, but Roberts says the social network's action here shows that veering into the territory of Nazi imagery is crossing a line.
Bobby Allyn, NPR News, San Francisco. Transcript provided by NPR, Copyright NPR.