Maybe the secret to longevity isn’t clean living or exercise, but anger. In its 13 years, “South Park,” the Comedy Central animated series, has thrived on a diet of vitriol — usually directed at it by the targets of its willfully crude satire. In recent seasons the show has taken aim at Tom Cruise and the Church of Scientology, Kanye West (before he imploded at the MTV Video Music Awards) and “Ava