That's stupid because iTunes store do actually sell South Park episodes.
Forget about explicit music, the South Park TV show itself is available in the iTunes Store, so it is pretty ironic that the South Park app would somehow be too offensive for Apple to sell.
Not to mention that Apple has featured South Park on their Pro - Profiles page.
http://www.apple.com/pro/profiles/southpark/
There's got to be more of a reason behind the objection other than being potentially offensive. Maybe some of the features were somehow too obtrusive to the OS.