"My baby, doing what I want with him"

Today I witnessed and even participated in a terrible incident on the way home. on the street young a man (father) beat boy (son). The boy was about 10 years old, cried a lot and it is not punished, but were just beaten.
I guess it was stupid, but I couldn't just walk by. I intervened and tried to reason with the man. I can understand that sometimes a child can be punished, but it is not permissible to beat it.
On my intervention the man reacted very aggressive, started yelling that it was his son and he can do whatever he wants with it.
Turned his attention on me, the man stopped beating the boy. I was very lucky that the street was passing guys on motorcycles and held a man. They intervened and I didn't get hurt.
The man threw some of his rage at not a boy, and we, the passers-by who defended the child. But, unfortunately, globally, we could do nothing to help the child. Scary to imagine what to do at home parents, if the father sincerely believe that the child is his property which can be arbitrarily obrashatsa. In Russia, there are no ways to protect children exposed to domestic violence. Living in such an environment that it will be in the future, it can not affect his psyche.
I am extremely sorry for children and women subjected to domestic violence. It is necessary not to pass by when we see this, to help, to protect those who are weaker and can't defend himself.