It's almost as if what you describe as mockery of Christianity is largely punching up at a secure and itself mildly- to significantly-onerous institution in the United States and that defense of Islamic people is an example of punching-down xenophobia aimed at individuals that's dressed thinly as "criticism of the religion".

If Christians were targeted by violence on American streets after 9/11 (as they were--along with, you know, completely unrelated Sikhs), "the left" would say that's wrong, too. And the reason that the status quo with regards to anti-Islam sentiment is what it is is because Americans in a whole lot of places genuinely haven't progressed much beyond that mindset.

There's a difference of kind here.