They tried in the “Carton Wars” episode. Comedy Central would not let them show a pic of Mohammed. The part where Mohammed showed up was cut out and there was a black screen that said “Comedy Central would not allow us to show a picture of Mohammed or some message to that effect. It was a big deal at the time.
Never forget the silence of the self described bravest of Hollywood when two of their own were actually threatened with death. I don’t remember George Clooney speaking up for free speech in this case, although he loves to pretend Hollywood somehow garners credit for civil rights.