Some perspective....
Be thankful wherever your son is. Be most thankful that he is a vibrant, healthy boy. My son got called up late to varsity his sophomore year, got no playing time whatsoever, and yet, we were beside ourselves with joy. He played for the largest public high school in the state of Ohio and even making the freshmen team was an achievement let alone getting playing time on varsity as a sophomore. I never advised him one time in his career to talk to the coach. The coach speaks to the team with the lineup card. The player will not change that decision based on verbal argument.
Look, this whole topic and debate boils down to control. Control the things you can control and let go of the things you can't. This will take the 800 lb. gorilla off you and your son's shoulders.
What you absolutely CANNOT control:
Coach's decision
What you CAN control:
1a) Your attitude
1b) Your effort
Focus on the what you can's and let go of the what you cannot's. It will simply your life and lead to ultimate happiness. Now encourage the young man to get to work and have the best attitude on the team. Encourage him to do this while keeping his mouth shut. Someone will eventually notice.