i have never watched this program, but something tells me they dont mock islam like they do the virgin mary.
you have insight while you say you come to this conclusion by not watching the program.
may i recommend watching the program, or at least reading scripts, before coming to conclusions.
To quote someone that once commented on the issue of South Park: "It's only funny when they're mock people, politicians, and religions I don't like, because it's so true."