I don't see an explanation under illegal acts that's justifies being ejected from a game for performing the Cam Newton celebration. The ripping the shirt open jester is more of an immediate celebration description under legal acts.
As I said, I don't have a problem with rules or teaching sportsmanship, I do however have a problem with not injecting common sense within the rules.
there is nothing in the superman TD celebration that constitutes such a punishment.
Honestly I'm probably not the best person to explain why they chucked the kid simply because if I was in charge Id ban any and all celebrations that take place in the field of play.
You want to celebrate? Do it in the team box with your team mates, but anything that takes place on the field would be subject to at least a 15 yard penalty and an ejection if it was flagrant enough.
Is it overkill? Maybe, but its also the only rule that would make it fair across the board and remove and judgment calls on whats acceptable and whats not.