because they’re basically just making it as undeniable as possible that he revels in being a piece of shit
You'd think that forcing a kid to unknowingly eat his parents' remains, then licking his tears; smiling at a video of the 3rd reich (which was supposed to make him learn that nazism was bad) and dressing as hitler; yelling "FUCK JESUS!" in front a christian crowd just because he lost a bet, there would already be loads of undeniable proof of how much Cartman's a piece of shit (lovable as a character, terrible as a real human)