The left views Muslims as a minority victim class. Their "intellectuals" at university's have little to no negative things to say about Islamic nations or any of the followers of the faith. The left is a big herd, following a handful of peeps.

If Islam was the majority religion in the US, maybe the left would critique it.

Generally, they had a bad experience with Christian churches or persons at some point in their life. It is both politically correct and seen as a badge of honor among leftist "intellectuals" to oppose Christianity. Part of that is their poor experience, part of it is their lack of understanding of the texts and history. Leftists have shit grasp on history in general.