My advice is that whether you not it or not, you seem like you are being "that dad". I would back away and have the boy meet with the coach. The coaching fraternity is so small, that you don't want a negative feeling out there in regards to your son, or you. Both could be detrimental to your son.
From some of the posts above, I think your son is partially responsible for the negative relationship with the coaches. He needs to make it right with them and conform to the rules of the team. If he cannot do that, he needs to go somewhere else. It is apparent to me that if the coach has the sour reputation that you mentioned, the administration is not going to do anything about it. Why would I think that? Because if you feel the need to approach the coach, don't you think that others have gone to the coach and the administration before?