They have.
Trey and Matt submitted shows to Comedy Central (which runs their show) depicting Muhammad but the channel either censored or bleeped much of that content. Stone said about the whole incident:
I think Comedy Central totally f****** ****ed out. Now, they werent any different than anyone else, so its not like you can single them out. But I think it wouldve been an important statement for one media outlet in America to stand up. That was one of my most disappointing moments as an Americanthe American presss reaction to the Muhammad cartoons. It was completely wimpy. Cartoonists, people who do satirewere not in the army, were never going to be f****** drafted and this is our time to stand up and do the right thing. And to watch the New York Times, Comedy Central, everybody just go No, were not going to do it because basically were afraid of getting bombed sucked. I was so disappointed.
Yea, the show is crude and just wrong at times. I find myself turning it off not infrequently. It is also at times brilliant. It is hard to paint the show with a broad brush - libertarian is more right than wrong - but this exchange sums it up nicely:
Q: Are you two guys liberal or conservative? Me and my friends have had debates about this.
Parker: We avoid extremes but we hate liberals more than conservatives and we hate them [conservatives].
Stone: I hate conservatives but I really f****** hate liberals.
There are other shows I'd avoid before South Park. Your mileage may vary.