Members of the controversial Westboro Baptist Church protest outside a prayer rally in Houston in 2011. (Richard Carson/Reuters)

Millions of Americans support free speech. They firmly believe that we are the only country to have free speech, and that anyone who even questions free speech had damn well better shut the #$%& up.

Case in point: In a recent essay in The Daily Beast, Fordham Law Professor Thane Rosenbaum notes that European countries and Israel outlaw certain kinds of speech—Nazi symbols, anti-Semitic slurs, and Holocaust denial, and speech that incites hatred on the basis of race, religion, and so forth. The American law of free speech, he argues, assumes that the only function of law is to protect people against physical harm; it tolerates unlimited emotional harm. Rosenbaum cites recent studies (regrettably, without links) that show that "emotional harm is equal in intensity to that experienced by the body, and is even more long-lasting and traumatic." Thus, the victims of hate speech, he argues, suffer as much as or more than victims of hate crime. "Why should speech be exempt from public welfare concerns when its social costs can be even more injurious [than that of physical injury]?"

I believe—strongly—in the free-speech system we have. But most of the responses to Rosenbaum leave me uneasy. I think defenders of free speech need to face two facts: First, the American system of free speech is not the only one; most advanced democracies maintain relatively open societies under a different set of rules. Second, our system isn't cost-free. Repressing speech has costs, but so does allowing it. The only mature way to judge the system is to look at both sides of the ledger.

Most journalistic defenses of free speech take the form of "shut up and speak freely." The Beast itself provides Exhibit A: Cultural news editor Michael Moynihan announced that "we're one of the few countries in the Western world that takes freedom of speech seriously," and indignantly defended it against "those who pretend to be worried about trampling innocents in a crowded theater but are more interested in trampling your right to say whatever you damn well please." To Moynihan, Rosenbaum could not possibly be sincere or principled; he is just a would-be tyrant. The arguments about harm were "thin gruel"—not even worth answering. Moynihan's response isn't really an argument; it's a defense of privilege, like a Big Tobacco paean to the right to smoke in public.

In contrast to this standard-issue tantrum is a genuinely thoughtful and appropriate response from Jonathan Rauch at The Volokh Conspiracy, now a part of the Washington Post's web empire. Rauch responds that

painful though hate speech may be for individual members of minorities or other targeted groups, its toleration is to their great collective benefit, because in a climate of free intellectual exchange hateful and bigoted ideas are refuted and discredited, not merely suppressed .... That is how we gay folks achieved the stunning gains we've made in America: by arguing toward truth.

I think he's right. But the argument isn't complete without conceding something most speech advocates don't like to admit:

Free speech does do harm.

It does a lot of harm.

And while it may produce social good much of the time, there's no guarantee—no "invisible hand" of the intellectual market—that ensures that on balance it does more good than harm. As Rauch says, it has produced a good result in the case of the gay-rights movement. But sometimes it doesn't.

Europeans remember a time when free speech didn't produce a happy ending. They don't live in a North Korea-style dystopia. They do "take free speech seriously," and in fact many of them think their system of free speech is freer than ours. Their view of human rights was forged immediately after World War II, and one lesson they took from it was that democratic institutions can be destroyed from within by forces like the Nazis who use mass communication to dehumanize whole races and religions, preparing the population to accept exclusion and even extermination. For that reason, some major human-rights instruments state that "incitement" to racial hatred, and "propaganda for war," not only may but must be forbidden. The same treaties strongly protect freedom of expression and opinion, but they set a boundary at what we call "hate speech."

It's a mistake to think that the U.S. system goes back to the foundation of the republic. At the end of World War II, in fact, our law was about the same as Europe's is today. The Supreme Court in Beauharnais v. Illinois (1952) upheld a state "group libel" law that made it a crime to publish anything that "exposes the citizens of any race, color, creed or religion to contempt, derision, or obloquy." European countries outlawed fascist and neo-Nazi parties; in the 1951 case Dennis v. United States, the Supreme Court upheld a federal statute that in essence outlawed the Communist Party as a "conspiracy" to advocate overthrowing the U.S. government. Justice Robert H. Jackson, who had been the chief U.S. prosecutor of Nazi war criminals, concurred in Dennis, warning that totalitarianism had produced "the intervention between the state and the citizen of permanently organized, well financed, semi-secret and highly disciplined political organizations." A totalitarian party "denies to its own members at the same time the freedom to dissent, to debate, to deviate from the party line, and enforces its authoritarian rule by crude purges, if nothing more violent." Beauharnais, Dennis, and similar cases were criticized at the time, and today they seem grievously wrong. But many thoughtful people supported those results at the time.

U.S. law only began to protect hateful speech during the 1960s. The reason, in retrospect, is clear—repressive Southern state governments were trying to criminalize the civil-rights movement for its advocacy of change. White Southerners claimed (and many really believed) that the teachings of figures like Martin Luther King or Malcolm X were "hate speech" and would produce "race war." By the end of the decade, the Court had held that governments couldn't outlaw speech advocating law violation or even violent revolution. Neither Black Panthers nor the KKK nor Nazi groups could be marked off as beyond the pale purely on the basis of their message.

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.