I think that's a problem here. An offensive joke is being dressed up as a gender issue. There isn't a gender issue here, there's just a maturity issue with everyone involved.
Who decides what's the real abusive situation? I suspect the victim. It's not possible for a third person to objectively know, it can only be guessed in which case some kind of "decision" is necessary. Sorry, but what is a bystander to do? You are upset because he decided something was abusive and acted. I guess you would be happier with inaction? I don't understand.