Baseballmom,
I dont think that others mean to be hard on you, for me, as a mom I know how we want to protect our young, its instinctive, but I can tell you from experience that if you get on his case while in HS, it will be easier later on. Most college programs will not put up with attitudes so better to adjust it now. Maybe the coach is letting your son know in his own way, improve or you wont play for me in the spring.
FWIW, when my son was being recruited by a particular program one of the players (a first round pick out of HS) was strongly trying to sell himself to this same program. The coach told me later on that there was no way he would offer that player, even though he knew he would be drafted and most likely one of the most talented he saw that year, he wasnt taking any chances, he did not appreciate his attitude.
Also throughout my sons 3 years of college, I had seen a player or two asked to leave because they just were not "team" players. Keep in mind that is VERY important in the college game to not come with an attitude that you are better, or that the coach turned into an idiot, or is against you, or he should be acting more like the adult, because by 18 your son IS now an adult and responsible for his actions and attitude.
You can think that all you want, but it has to not ever be related to those that will determine whether you play or not. NEVER.
Also stop feeding the wolf, by letting your son think he is better than anyone else. Parents need to step back, only time you have a say is when your player is hurt.
Good luck.