Those decisions paved the way for triumphs by civil rights, feminist, and gay-rights groups. But let's not pretend that nobody got hurt along the way. The price for our freedom—a price in genuine pain and intimidation—was paid by Holocaust survivors in Skokie and by civil-rights and women's-rights advocates subjected to vile abuse in public and private, and by gay men and lesbians who endured decades of deafening homophobic propaganda before the tide of public opinion turned.
Free speech can't be reaffirmed by drowning out its critics. It has to be defended as, in the words of Justice Oliver Wendell Holmes, "an experiment, as all life is an experiment."
I admire people on both sides who admit that we can't be sure we've drawn the line properly. In Dennis, the case about Communists, Justice Felix Frankfurter voted to uphold the convictions. That vote is a disgrace; but it is slightly mitigated by this sentence in his concurrence: "Suppressing advocates of overthrow inevitably will also silence critics who do not advocate overthrow but fear that their criticism may be so construed .... It is a sobering fact that, in sustaining the convictions before us, we can hardly escape restriction on the interchange of ideas." When Holmes at last decided that subversive speech should be protected, he did so knowing full well that his rule, if adopted, might begin the death agony of democracy. "If in the long run the beliefs expressed in proletarian dictatorship are destined to be accepted by the dominant forces of the community," he wrote in his dissent in Gitlow v. New York, "the only meaning of free speech is that they should be given their chance and have their way."
The reason that we allow speech cannot be that it is harmless. It must be that we prefer that people harm each other, and society, through speech than through bullets and bombs. American society is huge, brawling, and deeply divided against itself. Social conflict and change are bruising, ugly things, and in democracies they are carried on with words. That doesn't mean there aren't casualties, and it doesn't mean the right side will always win.
For that reason, questions about the current state of the law shouldn't be met with trolling and condescension. If free speech cannot defend itself in free debate, then it isn't really free speech at all; it's just a fancier version of the right to smoke.