[philwelch]

Actually, platforms that de-platform tolerant platforms like Gab are the real intolerant ones.

I'm being (slightly) facetious, but the point is that Popper's argument, or at least this naive interpretation of it, can be used to justify any intolerance. There's no obvious reason you can't use Popper's argument to justify McCarthyism or the Muslim ban or even Japanese internment on the grounds of the alleged intolerance of their intended targets, or the existential threat they posed to liberalized society. In fact, most actual justifications of those things are based on Popper's argument; it's of the same species as "the Constitution is not a suicide pact" or "are you going to convict Jack Bauer?". This is literally how people tried to justify every violation of civil liberties in American history.

US judicial precedent around the First Amendment has varied over time. The hoary cliche that "you can't shout fire in a crowded theater" comes from a Supreme Court ruling in 1919, Schenck v. United States, that the First Amendment did not protect advocacy of draft resistance. That ruling was overruled, and the standard set by the court in 1969, in Brandenberg v. Ohio, was "imminent lawless action". And I think that standard meets Popper's bar without the risk of it devolving into totalitarianism for the sake of protecting us from totalitarianism. Which, incidentally, has been the sales pitch of every totalitarian regime ever. The next batch of Nazis are going to get power by telling us they need it to protect us from the Nazis.