1) Work out
2) Take out your violent tendencies through boxing, as you clearly have some pent up aggression. This is quite normal.
3) (What you should do in a perfect world but technically should not) – If you ever do see a man beating a woman or child, sucker punch that man in the side of head. Keep kicking them when they are down and then run before the police get there.
4) (What you should do in a country dominated by ligation and British law) – Alternatively you could try usng reasonable force but this might end up with you getting your head kicked in or your throat slashed.
5) (What I wouldn’t fault you for doing) – Learn that the world is a sad place and just intervene as you can…. without risking your self (this is more than most people do)….. If you get killed, what will your family do. Do things that protect the victim, but minimize risk to yourself. Shouting loudly and calling the attention of passers by is a good one.
Have a nice day.