Why is there still a stigma against men hitting women...?

Why do men have to only see equality as being about physical strength? A person can be strong and capable mentally. I don't see why either gender wants to knock the crap out of each other. Not only that, elderly, the very young and disabled men and women get bashed up so how can anyone have the nerve to exert their physical strength over the obviously weaker people. Why is being all tough so cool if you bash someone senseless just to prove a point?