If you’re still unfamiliar with Rutger Bregman, you likely won’t be for long. Last month, the Dutch historian and author went instantly viral after imploring the world’s financial elite to pay their fair share in taxes during a panel discussion at Davos. “We can’t talk for a very long time about all these stupid philanthropy schemes,” he said at the time. “But come on, we’ve got to be talking about taxes. That’s it, taxes, taxes, taxes. All the rest is bullshit in my opinion.”

The screed earned him an invitation to “Tucker Carlson Tonight,” but his segment with the eponymous Fox News host and darling of the alt-right never aired. Now we know why. In new audio released by Now This, Carlson can be heard telling his guest that he has a “tiny brain” and that he should go “fuck himself”—this for pointing out that the television personality is, in Bregman’s words, “a millionaire funded by billionaires.”

“I hope this gets picked up because you’re a moron,” Carlson bleats. “I tried to give you a hearing, but you were too fucking annoying. …”

The interview begins innocently enough. Carlson tips his proverbial cap to Bregman for challenging the audience at Davos, chuckling at the hypocrisy of those who feign concern about climate change and economic inequality while flying private jets and hiding their money in offshore accounts. But the mood quickly changes when Bregman prods the television host about his network’s willingness to scapegoat immigrants and people of color.

“I’m glad you’re finally raising the issue,” he says, “but that’s what’s been happening for the last couple of years.”

“And I’m taking orders from the Murdochs, is that what you’re saying?” Carlson shoots back.

“No, it doesn’t work that directly,” Bregman answers. “But, I mean, you’ve been part of the Cato Institute, right? You’ve been a senior fellow there for years? You’ve been taking their dirty money.”

The conversation would only devolve from there, with Carlson unloading on Bregman and Bregman returning in kind. “[You’re jumping] on the bandwagon of people like Bernie Sanders and AOC,” the historian says in one pointed exchange. “But you’re not part of the solution, Mr. Carlson. You’re part of the problem, actually.”

Listen to the heated exchange below:

Watch Fox News host Tucker Carlson call one of his guests a ‘tiny brain…moron’ during an interview. NowThis has obtained the full segment with historian Rutger Bregman that Fox News is refusing to air. pic.twitter.com/kERYPUaGLY — NowThis (@nowthisnews) February 20, 2019

Update: Tucker Carlson has issued a response to Now This’ reporting, claiming that his use of profanity was the reason the segment never made it to air. Carlson apologizes for his foul language, but true to form, he insists that his word choice was “entirely accurate.” Watch: