The other thing about relativism is that it pretty much means that the other person's opinion is always just as valid as yours: even if you don't agree with them. Maturity and puberty are not relevant.
"Don't be evil" uses a word that means different things to different people, by definition: "evil". Using such a word means that you invite others to judge you by their own criteria. Likely, if your criteria correspond to theirs, you'll like them much more. If the criteria don't match, you'll like them much less.
Schmidt's statement seems like an appeal to relativism - an attempt to make the statement meaningless, because they don't want to be morally judged any more. Fine. Perhaps, they don't want to be morally judged any more because there are a lot more people that disagree, as evidenced by various comments in this thread.