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On his show last night, Tucker Carlson battled an Antifa activist over free speech and political violence.

Antifa - or "anti-fascist" - groups have made headlines in recent months for violently protesting conservative or alt-right events, perhaps most infamously Milo Yiannopoulos' speech at UC-Berkeley in February.

Mike Isaacson, a professor at John Jay College of Criminal Justice and founder of Smash Racism D.C., argued that Antifa activists have the right to respond to violence with violence.

Carlson said Isaacson is "blurring the lines" between physical violence and speech with which he disagrees.

"You're conflating violence with ideas," Carlson said. "If I have not raised my hand to strike you, you have no right to strike me."

He asked Isaacson if he teaches his students that the First Amendment does not apply to people they disagree with.

"I teach them to think critically, and that's why I'm very open about my anti-fascism and my anarchism," Isaacson said, adding he has had students who were Trump supporters or members of the alt-right and he held them to the same standards as any other student.

"I don't believe you," Carlson fired back.

Following the interview, the NYPD's largest police union noticed a tweet from Isaacson last month, in which the professor called it a "privilege" to "teach future dead cops" at John Jay College.

“Michael Isaacson harbors total disdain for the active and future police officers that he teaches at John Jay College,” PBA president Pat Lynch responded, to the New York Daily News.

Additionally, Rep. Dan Donovan (R-N.Y.) called for the CUNY school to fire Isaacson.

Watch the back-and-forth between Isaacson and Carlson above.

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