Fox News host Jesse Watters reported Sunday on self-proclaimed anti-fascist groups, commonly known as "antifa," conducting an interview with what he believed was a leader of a group. But unbeknownst to him at the time, he was speaking with a known, self-identified troll.

Watters took issue with what he saw as advocacy for violence in the essay, which reads in part, "It's time for liberals and progressives to lose their illusions about the anarchist movement and our tactics because, quite frankly, you have no one else willing to fight for you."

Watters began the segment by reporting on an editorial from the anarchist website It's Going Down, titled " An Open Letter To Liberals & Progressives From The Black Bloc. " The Black Bloc is a protest tactic, often employed by anarchists, where protesters dress in all black clothing to obscure their identities from authorities.

There to defend the op-ed was its alleged author, "Kevin," who also goes by the username BG Kumbi on YouTube and Twitter . He told Watters he represented antifa in Boston.

But according to It's Going Down, Kevin didn't write the article. Nor does Kevin represent antifa in Boston.

When asked if he wrote the op-ed, It's Going Down said on Twitter, "No, not at all. He's a pro-Trump troll." The site also posted an article describing the group Kevin claimed to be a part of, Boston Antifa, as being run by a pair of "alt-right trolls" in Eugene, Oregon.

Some aspects of Kevin's appearance on Fox were inconsistent with previous antifa behavior online and at protests. In the interview, Kevin said that CNN "basically doxxed" the Reddit user who originally made the controversial Trump-CNN wrestling video, a position popular among the online pro-Trump community. Anarchist activists using black bloc tactics at protests also typically shun media attention, wearing black masks to conceal their identities.

It's Going Down said it had received dozens of death threats since Kevin's interview on Watters' World. The site said that an interview on another Fox News show, Tucker Carlson Tonight, had a similar effect when host Tucker Carlson invited Heat Street's Ian Miles Cheong to talk about antifa.

Kevin has posted trolling videos to his YouTube account mocking progressive ideas.

In one titled, "I joined antifa," he mocks progressives on the issue of race.

"I declare this officially: I joined antifa, I'm gonna bring about a communist revolution, and make white people go extinct," he says. "Actually, race is a social construct, and there’s no such thing as white people, but they exist and are evil and oppress other races, which also don’t exist but also do at the same time. This is what we call doublethink here at the gulag. It’s when your brain is so powerful you can actually hold two different, conflicting ideas at the same time."

One person who may have been watching the interview: President Trump.

Philip Rucker, the Washington bureau chief of the Washington Post, tweeted that he and other reporters saw the president watching Watters' World aboard Air Force One the same night Watters' interview with Kevin aired.