Are you a monster? Doesn't sound so, in fact, just the opposite. Of course, YOU saying "no" may lead to rebellion.
I keep asking when high schools will drop football, and I'm pretty certain it's going to be soon. Insurance will rise, due to documented risk, and with it programs will disappear.
It stinks he's been doing it for so long, and that he excels in the sport. That is the tough nut.
Good luck, I don't envy your situation. Often we hide the obvious truth due to confrontation or inconvenience.