What do you expect the outcome to be of you talking with the coach? Do you think its going to change his mind? Do you think he will change his coaching style? Most likely no to both of these situations. Will it make you feel better? Probably, but I think it could have a very negative effect. Hopefully he is not the type of coach to take the transgressions of the parents out on the kids, but you never know. Talking to him could do more harm then good.
If it were my son, I would suggest he approach the coach, outside of the baseball setting. Tougher to do in the summer, but if it was the school year I would suggest he set an appointment with him during the school day and go talk with him. Don't be confrontational, but rather inquisitive. Ask him what he needs to work on to improve his game. Don't ask what he needs to do to get in the lineup, but rather what he needs to work on. If they coach provides decent feedback, then make sure your son works 200x harder on those things then the other players around him. Hopefully the coach will come around, if he does not you still have the satisfaction of knowing you worked harder then anyone else.
If the coach is not receptive to the discussion, then your pretty much SOL and need to accept the situation, or look at moving on.