Flies in the face of good taste -- it's a sensory assault that all ends up feeling like a test of endurance, really. How much tastelessness can you endure, viewer? And yet, it addresses issues of paternal scapegoating, the MPAA's unscrupulous fuckery and xenophobia with wit and charm. UN-PC in a way so sneakily admirable it keeps you coming back.
Well, it's South Park, is that enough? I guess yes, it's probably the best comedy series ever made and this is... the movie (I don't think it's as good as most of the episodes from the series, but, still, it's awesome!). It's great how they fill this with dark comedy and don't really care about bubblegum comedies, as comedies usually do, and they also fill it with cricticism, and that's why South Park is so good.