And as long as I'm disagreeing with Glenn Reynolds, let me say that I disapprove of "Everybody Draw Mohammed" Day, which he seems to be promoting. (Hot Air, Dan Savage, and Reason are actively delighted by the idea.)
I have endless contempt for the threats/warnings against various cartoonists who draw Muhammad (or a man in a bear suit who might be Muhammad, but is actually Santa Claus). But depictions of Muhammad offend millions of Muslims who are no part of the violent threats. In pushing back some people, you also hurt a lot of people who aren't doing anything (other than protecting their own interests by declining to pressure the extremists who are hurting the reputation of their religion).
I don't like the in-your-face message that we don't care about what other people hold sacred. Back in the days of the "Piss Christ" controversy, I wouldn't have supported an "Everybody Dunk a Crucifix in a Jar of Urine Day" to protest censorship. Dunking a crucifix in a jar of urine is something I have a perfect right to do, but it would gratuitously hurt many Christian bystanders to the controversy. I think opposing violence (and censorship) can be done in much better ways.
At the same time, real artists like the "South Park" guys or (maybe) Andre Serrano should go on with their work, using shock to the extent that they see fit. Shock is an old artist's move. Epater la bourgeoisie. Shock will get a reaction, and it will make some people mad. They are allowed to get mad. That was the point. Of course, they'll have to control their violent impulses.
People need to learn to deal with getting mad when they hear or see speech that enrages them, even when it is intended to enrage them. But how are we outsiders to the artwork supposed to contribute the the process of their learning how to deal with free expression? I don't think it is by gratuitously piling on outrageous expression, because it doesn't show enough respect and care for the people who are trying to tolerate the expression that outrages them.
UPDATE: More here.