Harvard Law School Professor Emeritus Alan Dershowitz on Wednesday condemned Fox News host Tucker Carlson for saying mass illegal immigration makes the U.S. “dirtier.”

“I hate boycotts and attempts to censor free speech. I’m in favor of complete dialogue but, as such, I feel compelled to tell you that I, with due respect, disagree with the way you categorize mass immigration,” Dershowitz told Carlson during Wednesday night’s episode of the anchor’s show.