"If You Want To Combat Hate, Don’t Outlaw Hate Speech—Counter It With Better Ideas" by James Kirchick was recently published in Tablet magazine. Quote: "by marking certain speech as politically taboo, the European political establishment has strengthened marginal voices. 'Outlawing the NPD will spare German society having to confront right-wing extremism,' Anetta Kahane, an anti-fascist activist, told the German magazine Der Spiegel last year. 'You won’t get racism out of people’s heads by banning the NPD. You’ve got to confront their attitudes.' In other words, the best weapon to combat offensive and stupid speech is intelligent, nuanced speech."
In the context of the jailing of Holocaust denier David Irving in Austria, Kirchick says: "banning Holocaust denial and throwing those who espouse it into jail hasn’t diminished the political inheritors of Austrian fascism. In fact, prohibiting public expression of neo-Nazism comfortably coexists with widespread nostalgia for Nazism."
I'm very convinced that besides the reasons above, free speech also means that no one gets to determine which ideas are acceptable, and which ones are taboo. In Arizona now, there's an effort to allow the owners of public establishments like bakeries, bars, and motels to discriminate against groups like gays if they claim that their religious ideas dictate this bigotry. Of course this is one step beyond speech, but I think banning speech would only encourage such violations of other people's rights.
Update February 25: