> free speech and avoiding censorship are not just legal rights, they are principles that ought to be defended. those who would argue for a world where the de facto standard is censorship because they are capable of a narrow legalistic interpretation of freedoms are hideously short-sighted. if you endorse the erosion of these principles in the venues where you are strong, your enemies will use your exact arguments to erode them where you are weak.
Although I agree with your general sentiment, I think you're being a bit bullish. It's important to understand what, exactly, we mean by "free speech". John Stewart Mill's On Liberty is the starting point for any such discussion.
In the essay, he discusses "freedom of thought" in this very famous paragraph:
But the peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.
The idea of freedom of speech isn't simply that "anything goes." In fact, the Supreme Court has upheld this position many (many) times: see Chaplinsky v. New Hampshire for the canonical example. Preventing shitposting on 4chan or on Yik Yak is not (I repeat: NOT) an infringement of free speech. There are no veritable opinions there. There is nothing that deserves the invokation of Mill's freedom of thought. In other words, there is nothing of value.
Note that this distinction contrasts with something like Bill O'Reilly's The Factor or your annoyingly conservative grandfather, whom you may disagree with, but who also might have some insight.
But there are some things which we've resolved: we know that Nazis had it wrong, we know that racism is immoral, we know that we landed on the Moon. So not giving a platform to anti-Semites, racists, or flat-Earthers is not an infringement of free thought, as Mill described it.