If you are banned for letting a guy talk about underage play, that is on you and your fault. Even without it being a zero tolerance rule, you should know it's wrong and should tell anyone to shut up and ban them immediately.
I would have thought this was common knowledge and logic.
Things like this are zero tolerance which mean you are banned forever, and that means "forever". So give up, move to another site and don't repeat the same mistake, everywhere has this zero tolerance rule, so don't let anyone else risk your account if you go to another site.