IMO the line is drawn at not making it personal. Coaching hard is fine - in fact there are times when it’s necessary. Mocking or belittling a player is not fine. I know that some coaches do it and I don’t understand how they don’t know they are out of bounds. I worked under a coach that was guilty of that behavior and I couldn’t stand it. A lot of what I did was following behind him to clean up the messes he made. It’s an indication of a program that doesn’t have a good culture. And coaches that behave poorly usually have a reputation for doing so if you don’t personally witness it yourself. I have never known it to be a secret - or even something that was difficult to find out. IMO opinion you are more likely to encounter this in Junior College than anywhere else. There is usually zero oversight in JuCo programs so as parents and players you have to really vet the HC of any program you are considering. This is true at every level of baseball but especially true in JuCo.