Big JW,
Let me ask you this, if the coach is getting into your sons head so much that it starts spilling into the classroom and affecting his grades would you talk to the coach. If it started causing your son to retreat into a shell would you talk to the coach.
There are those here who say "it's part of the growing up process", it might be for their child, but this is your kid, he is different from other kids. My son is a sophomore in college and he still has trouble approaching coaches, he will do it when he is comfortable doing it.
My personal opinion is the coach is a teacher, the teacher should have an open door policy as long it's not about playing time. If it's something that really bothers you and you are afraid that it really is affecting your son mentally, why wouldn't you politely set up a meeting with the coach and nip this in the bud before it affects your son in other areas.
Bottom line is this is a great place to get info and you are going to get various opinions and feedback. But as a parent, you know your son better than any webster or coach and it's your responsibility to make sure your child is not being harmed either physically or mentally by anyone. It's your call!