I think this is about the tolerance paradox: you can't tolerate the intolerant, lest you lose your tolerant space. Not a fun thing to discuss, but it has to be discussed and enforced nevertheless.
~softwarepagan: I think you got the wrong idea; they're not talking about everyone caring about free speech being fascist, they're talking about what happens when fascist invoke free speech. Typically, fascists will use rebuttal from small communities to argue for wider bans against wider groups of people. E.g. someone might get kicked from a meeting for being a dick, and they'll use that to argue for university-wide bans against safe spaces.
Where you draw the line is eminently subjective and debatable, but you've got to do it.