I agree for the most part, though, after Littlefoot does a bit more than the usual rule breaking in my LBT 16, he does get grounded for a week from seeing his friends, which, considering how he snubbed them in that one, will make him value them more and hence can serve a purpose.
I guess if the punishment can serve a purpose at the end, it's ok, but, otherwise, if not, keep it out of the ending, you're right there.