That still doesn't change why one can't employ a small amount of awareness. While Jesus and God and et cetera are depicted, most direct ridicule goes towards actual priests, rabbis, or whatever the bigot de jour is up for mockery. Whereas it tends to be all or nothing when it comes towards Islam. Which is odd because directly attacking the people doing something bad is usually a more effective tool if one is not setting out to demonize an entire faith, as well as not drawing anything like the same controversy.
Also note that the depictions of Mohammad subject to recent controversy, excepting maybe the one from South Park just due to how very little screen time he gets, tend to be about as far away from 'religious figure mourning violence done in his name' as you can get. Most of it tends towards what would be offensive regardless of who it was, if not showing Mohammad directly causing the attack. There's no sympathy, just a direct xenophobic attack.