Stewart appeared on a periscope with Mike Cernovich shortly after he was fired from Donald Trump's campaign for organizing a protest outside of the Republican National Committee's headquarters.
Cernovich, who describes himself as "new right" but has been associated with the alt-right movement, is an online activist who regularly tweets inflammatory statements about race and sexual assault, as well as unfounded conspiracy theories.
One of his most controversial blog posts dismissed the existence of date rape. He wrote in a now-deleted tweet: "Have you guys ever tried 'raping' a girl without using force? Try it. It's basically impossible. Date rape does not exist."
In another tweet Cernovich later deleted, he said that "diversity is code for white genocide," a slogan frequently invoked by white nationalists. He also has said that people should "slut-shame" black women to prevent them from getting AIDS. He has also pushed conspiracy theories that the Orlando Pulse shooter did not act alone and that Hillary Clinton's campaign chairman was part of a sex cult.
During Stewart's appearance, Cernovich explained that he calls establishment Republicans "cucks" because "they like to see Trump get screwed over by the media, that's what they get off on." (The term "cuck" is an abbreviation of the word "cuckservative," an insult popular with the alt-right used to attack self-described conservatives who they view as too moderate.)
"Yeah, I would agree," Stewart responds, while laughing. (In a recent Reddit "Ask me anything" forum, Stewart responded affirmatively when asked if Virginia Gov. Terry McAuliffe was a "a cuck". He has also called his primary opponent Ed Gillespie "a cuckservative.")
Stewart, who was let go from Trump's campaign after organizing an unauthorized protest of women who supported Trump in the aftermath of the release of the "Access Hollywood" tape, also theorized in the October appearance that House Speaker Paul Ryan could have been behind the leak.
"I don't know what the source of that video is but I would not be surprised at all and if they were not source of it -- I would not be surprised if they knew that that was coming out," Stewart said.
Stewart defended his interview to CNN's KFile.
"Well look, if I get a call from a reporter or the new media, I'm gonna answer it, and I'm gonna talk to everybody, you know, I don't, I don't, I don't know anything about your past," Stewart said. "I'm not gonna interview you before you interview me, so just because somebody does an interview of me doesn't mean I support everything that they stand for."