I think that's precisely what they're saying: a lot of people talk about "free speech" because free speech benefits them. When you're in a dominant position, free speech doesn't threaten you. Or at least, you think it doesn't.

Few free speech advocates think you should be free to call for violence. That's free speech that does threaten them. Speech that calls for discrimination against groups they don't belong to, however, is perfectly fine -- they know that they're too important to be threatened by it.

So practically all self-described free speech advocates do put limits on free speech, and there aren't any True Scotsmen.