Coaches kicking their players in the back, or punching them in the head, is unacceptable.
That's a given, right? That a superior assaulting a subordinate is wrong? That these power dynamics discourage any pushback, because the victim risks a reduction in playing time, outright removal from the team or escalating physical and mental abuse under the guise of "hard practices?"
Bill Peters punched and kicked two players with the Carolina Hurricanes. It might not be the primary reason he's no longer coaching the Calgary Flames, but it was a contributing one.