Now why has the far-left decided that any criticism against Islam right or left is, well bigoted. Because Islam is not Christianity and Muslims tend to be something other than Caucasian and especially don't tend to be Anglo or of Western European decent. There are Caucasian-Muslims, but they tend to come from Eastern and Southeastern Europe, like in the Slavic countries. In the small fringe world of the far-left, maybe 10-15 percent of the population, its perfectly acceptable to criticize the Christian-Right, especially Caucasians. But if you attack a non-Christian, non-western religion, you are a bigot.
The far-left or fascist-left with their whole political correctness movement has decided that outlawing speech they find offensive, is simply not practical. The whole First Amendment gets in their way on that. So what they've decided that if they can't shut people up through government force, they'll try to shut people up through protest and lawsuit and screaming at people, to prevent people even on the Left like Sam Harris and Bill Maher, from making their case.