Bystander responsibility

I was part of an interesting dinner party conversation the other night about the responsibility of being a gym goer, a gym owner, or a gym employee. The talk was about one's responsibility when seeing someone who is doing something dangerous. Though we mentioned things like bad form and lifting too much weight or general overexertion, what the conversation really turned to was eating disorders. As a gym employee (kind of--I teach a couple of classes so I am more of a contracted employee) I was asked what our gym's (many of us go to the same establishment) policy was regarding confronting people with eating disorders. I doubt there is one. I know of other gyms that will discontinue a membership when they feel someone is engaging in disordered behavior. But that doesn't seem very productive either. Some other establishment will be eager to take that person's membership fees--probably my gym.
We didn't come to any kind of conclusion. I spoke rather abstractly about trying to create an environment--in my own classes anyway--that is about personal progress and actively eschews some of the dominant fitness discourses (working off that ice cream, mashed potatoes, brownie; working for tighter abs, toned thighs, etc.). Anyway, I left with a little more to think about.
But last night, I became quite disturbed by my bystander status and the previous evening's conversation really took on a new meaning.
Because last night I played tennis, actually at my gym's sister gym the next town over, next to a father hitting with his daughter. And it was disturbing. I know all about crazy sport parents, I watched that Bravo show several years ago. And I know about crazy tennis fathers--Mr. Dokic and Mr. Pierce to name just two.
But this guy was, I have no doubt, abusive. He was constantly berating his 9-year old (I am guessing her age--definitely younger than middle school). I heard one positive statement during the entire hour. But mostly it was negative statements that had a shaming tone to them; and that most definitely had a controlling tone. He told her to pick up a ball nearby to start a new rally. And then he yelled at her for not picking up the one he felt was closest to her. He questioned her committment if she wasn't jumping on her toes when he had a ball in his hand to start a rally. He packed up his racquet once and walked off the court about a half hour in leaving her to pick up the balls because he did not feel she was committed enough or paying enough attention or something. It doesn't matter, actually, because it was such a control move. he packed up again at the end of the hour leaving her to pack up the balls and racquets. Have I mentioned that this girl is 9? That she doesn't even play competitively (she told my doubles partner); oh and that the dad, who constantly corrected her form, was not that good of a player himself. She'll be better than him sooner rather than later. Perhaps this is part of the reason for his atrocious behavior. He may be pushing her away from the sport before she reaches that point.
And this happens every week according to my teammates. And apparently they have witnessed similar situations with other parents.
I was so angry and so sad. And so frustrated. What could I possibly do? Calling him out in front of his daughter would likely create a scene that would not be at all productive. No one I was playing with knew his name. We only know the daughter's first name.
I am thinking about reporting his behavior to the club manager. And I am thinking of contacting my friend who used to work for child services and asking about what is considered abuse.
But I am really at a loss. I think too often people stay out of situations like this because they feel it is none of their business. But I see this girl already steeling herself against his behavior and his words. We all realize, at some point, that our parents are human and not perfect; but 9 years old seems too young to see that your father is an ass.