“I’m like a shot a Levittown right in your ass, like a B-12 — boom!” Those were Jon Stewart’s last words to Bill O’Reilly in his guest appearance on Monday night’s O’Reilly Factor, in a virtuoso duel where comedy eviscerated farce. The two highly rated cable stars squared off over one of the more inane controversies in a political season full of inane controversies — whether the White House was wrong to invite the socially conscious rapper Common to perform at a poetry slam.