You seem to be making my case. If these parents really are so bad, then why post about it online?
I'd think that this would only make things that much clearer as to how to handle the problem.
The only way I could not see confronting them in person about this is if they were known to have a history of violence or some sort of criminal background, but then in that case they should have never had a place on the team.
Now that people have identified the coach and the parents I'd think the coach is now in the position of having to address this with his parents, and soon. The last time I looked at this thread it had over a thousand views in two days. I've got to believe at least some of these views are from parents of his team. I think many of whom who would probably wonder why the coach felt it was appropriate to address this issue concerning another parent on a public forum. I know that's what I'd be thinking.
File this thread under, "How not to handle a dispute with a parent on your team".
