This is the problem, why do you care?
You have your beliefs and thus anything anyone should say won't take them away from you, who cares if they mock your religion? People are mocked for everything, what they wear, how they act, what they think.
It's an insecurity because if Muslims were so in tone with their religion they wouldn't need to feel to defend it, let alone do it aggressively which some cases do.
In the case of Southpark, everything is mocked, all religions, all celebrities, Scientology, AIDs is even mocked. But when it comes to Muslims, it has to be censored. Oh no, we can't mock them, because if they do, they will get death threats from extremists. Doesn't that make the religion look good, huh?