"Muslims Ask French To Cancel 1741 Play by Voltaire", says a Pittsburgh Post-Gazette headline, but the body of the article also suggests that there was more to it than asking: "On the night of the December reading, a small riot broke out involving several dozen people and youths who set fire to a car and garbage cans."
Claiming that a play, even by a great writer, ought not be performed — as a matter of morals and manners, and not as a matter of law — because it's unfair to your group is not inherently troublesome. Some Jews, for instance, have said it as to the Merchant of Venice; I'm not that sympathetic to such objections, but neither do I see much reason to condemn them. But I don't recall any cars being burned on account of the play, or riots involving even a few people, much less several dozen.
As I've noted below, I'm skeptical about attempts to lay the problem at the door of "Islam" (or "Christianity" or "Judaism," as the case may be) in the abstract. But I can say that modern Islamic culture, especially in Europe and the Middle East, has very troubling strands within it, and strands that I suspect go far beyond just the several dozen people who happen to have been rioting here.
When Voltaire wrote the play in 1741, Roman Catholic clergymen denounced it as a thinly veiled anti-Christian tract. Their protests forced the cancellation of a staging in Paris after three performances — and hardened Voltaire's distaste for religion. Asked on his deathbed by a priest to renounce Satan, he quipped: "This is not the time to be making enemies."
Thanks to Peter Wizenberg for the pointer.