That's the "slippery slope" fallacy. There's a knee-jerk reaction in America that any censorship is bad and will somehow always lead to more censorship. But there area places where censorship has been implemented in small ways and it hasn't led to some sort of free speech apocalypse. In Germany or Israel, for instance, it's illegal to deny the holocaust. That's a pretty sensible limit considering their history. All these years later, they're still free an functioning democracies.