Great post and very in-depth. Thanks for you efforts. I am a Football (Soccer) coach at grassroots level and I have experienced some of the things you have presented.
Abuse in competitive sport is a massive problem and is taking it's toll in lots of ways. I have regularly seen Referees verbally and to a lesser extent physically abused by players, coaches and parents. In some cases the referees themselves we young people trying something new. The knock on effect of this is a lack of quality officials or even any officials for games. The ref's don't want the Hassel and the abuse and the children see this and do not consider becoming one themselves.
Children witnessing the abuse in a lot of cases consider it normal and 'part of the game'. Children are especially susceptible to the actions of the professional stars of their chosen sport but mostly by their parents. In my own experience, a child of an abusive parent will continue that trend with their own conduct, on and off the field.
I have taught Physical Education in schools and I coach football privately so I'm kind of split on the allocation of training children. Some schools have teachers with a wealth of experience and knowledge. For instance, my last school had a female squash champion (she was great at everything :) ), and an ex Premier league footballer. They were also good teachers. The problem is not all schools can match this kind of experience and knowledge but try to attain similar results. In a lot of cases good private coaching in a friendly, safe environment is the best option, again , not always available.
This is a subject very close to my heart so thank you for brining it up and writing such a brilliant piece on it. Gaz