That is indeed an interesting thing to think about.
We all know the best superheroes act differently than their alter-egos do. Think about when Kenny first took up the role; why did he do it? At some point he started using it to scare his parents into treating him and his siblings better, but he probably first started when he saw Cartman was doing it, and thought it would be a good idea because he really has a power, and because he knew it would make Cartman really mad.
Kenny is actually a really smart kid; this was his chance to take up a cause, to deny himself his natural impulses and weaknesses, to become a great and useful person, and to really piss Cartman off. Which was hilarious!