I was told by a father of a player on my sons team that he needed to be prepared to get his a$$ chewed out. I told my son the story and like Roothogg66 I told him it wasn't personal it is business, not to take anything said personal and if he would just sit back and think about what they are saying he would probably laugh about it. When fall practice started it was nonstop, there was nothing he did that was correct. One time the pitching coach took him and a teammate in to the weight room to show them how he wanted them to do a lift. The coach was showing the other player how to do his lift and my son sat in the seat of the machine that he was going to use, the coach turned to him and said, "Did I tell you to sit down!". My son jumped up, stood at attention and said no sir. The coach was still working with the other player and turned around a few minutes later and said to my son, "Are you ever gonna start your lift!". When he told me that I couldn't stop laughing. He said it wasn't funny and I told him it wasn't funny to him because he took it personally. Told him that the coach was trying to make him uncomfortable and wants to see how you handle all the "abuse". He wants to see how you handle pressure now not when he calls you to the mound with bases loaded no outs. He wants you to be comfortable being uncomfortable.
Son never told me anything else, but I have heard stories from other parents that would make you cringe. When I would tell my son and ask him if he heard anything he just says, I doubt it was said like that, and even if he did coach was just trying to get a reaction, player took it too personal. Amazing how attitudes change after 3 years.
Hope he can work through it, tell to not take it personally and keep working hard. If he can get through it he will probably have a different perspective in a few years.