Going to get into some psych here, but is your son in a roundabout way asking you if its ok to walk away from the program? If so you need to let him know that its his decision and you support him either way. Kids don't always ask but by letting you know he is having a hard time he maybe feeling you out to make sure you are going to be on his side if he leaves the team.
The above said, I ran track in college at a competitive school. The coach was a little old fashion and at times would be abrupt, distance and seem like he was ignoring you. My sr year I went to him with a problem with a class scheduling problem (he asked us to do this) that may cause me to drop below the required 12 credits needed in season. His answer to me, "figure it out its your problem" and he walked away. This really pi$$ed me off. I called one of the ACs that I was close with and let him know I was going to quit the next day. He talked me off the ledge and reminded me that the HC could be a little bit of an A.. and that I need to take 48 hours before making my decision. In the end it was good advice. I guess what I am getting at is this...Is there an AC that your son can talk to? It maybe that he is reading too much into things and that he is ok. The AC could maybe able give him some perspective.