At the end of the day if you are going to let a coach break you mentally, you were never going anywhere in the sport. Whether that means college baseball or just being a reliable varsity player. You can have all the talent in the world, but the truth is none of your teammates are going to want you on the field in the last inning if you let something as small as an angry coach discourage you. People tend to forget that there is a mental aspect to sports. HS sports are fun, but they're also competitive, it isn't supposed to be a feel good environment.
You will get nods and a lot of agreement from other parents when you tell them he's not starting or quit because the coach doesn't know what he's doing, but the truth is they are all rolling their eyes in the back of their heads. People can pick apart coaches all they want, but I'm sure that coach can pick apart something your kid doesn't do well to justify his decisions. Do we really want coaches to change what they are doing so one player can be encouraged a little more? Everybody (including starters) having problems with a coach is a coaching problem. One or two parents having a problem with a coach is a them problem.