You're probably right. The only things I've thought of doing is calling out the
coach to his face for doing that. I'm pretty non-confrontational though. So I would never choose to do that.
My other thought is to talk to the league president to try to get it so this coach can't keep coaching in the league (in future years). But I don't think the league would do that. No proof, plus it's hard enough to get parents to coach anyway.