Why would you call someone out on tipping behavior? It isn't that he groped the girl. Tipping is not a law. If he chooses not to tip, that's his business.
You may end up with egg on your face in the end - they will remember who triggered the charity event cancel - nobody will care why this heckling started and who is "right" or "wrong". No matter what the club manager says, I guarantee you he is not happy ...
IMHO the rule is to stay out of other people's biz unless there is something illegal taking place. Then just notify the authorities. Otherwise chances are you will end up with a bashed in face, keyed car, or a burning pile of **** on your front doorstep.
Sound familiar?
G