My son had a coach in middle school that consistantly was sarcastic to my son and often ridiculed him in public. Let me give you a for instance; 2 seconds left on the clock on an inbounds, my son asks for and receives the ball, but it goes through his hands, the coach sneers, "thanks for losing the game for us"
Throughout the season I didnt intercede but kept tabs on my son, asking him if he was ok with this coach. He said, "I can take it, he is like bobby knight". To me the coach was out of line and with a more sensitive player he could have taken out the joy for the game. If that coach had gotten into my sons head for no reason exept for the coaches frustration I would have been all over him, but I kept close tabs on my son and he was able to distinguish real instruction and even criticism from what was more often the coach's frustration.
There are ppl on this thread of both extremes. "coaches should never yell" etc to the others who say the coach is always assumed to be right. The truth most often lies in between these extremes.