Except that freedom of speech does not protect us from intolerance, as Karl Popper observed. For example, private entities are not required to uphold freedom of speech.
It's funny when Popper is brought up in this way because his conclusion was that the only reasonable censorship of intolerance was that which poses a threat of immediate physical harm. So basically how the US treats freedom of speech today.
He certainly wouldn't be supportive of censoring racist commentary that didn't incite immediate physical violence.
Funny enough, in Germany - which is definitely more restricted, and for good reason, on the US understanding of "free speech" - Facebook and Twitter are routinely seen as public discourse forums and have to unban users as long as what they post isn't against the law [1].
He certainly wouldn't be supportive of censoring racist commentary that didn't incite immediate physical violence.