HS coaches are human. Like other humans, some are deeply flawed, even disturbed, individuals. Yes, a player has to deal with this—life is like that and it pays to learn this lesson early. But to defend all coaches unconditionally (which some comments here come awfully close to doing) just isn’t realistic IMO.
I also believe that at some point (which is going to vary with circumstances, by kid, and by kids’ age) a parent ought to tell a child that “No matter what you do, you may not change this coach’s / teacher’s / boss’s mind.” The next part of that conversation needs to be about dealing with this fact in the right ways. But for my part, I think there are times when it’s not fair to a kid to just say “work harder, it’s all on you.”