The reality is, the cultural standard that stops men from hitting women actually causes women to be hit more often. As men, we learn early on that an act of aggression or violence initiated against another man will more than likely escalate and see us in a physical confrontation, this knowledge sees men avoid many unnecessary fights.
Women on the other hand are told they can use violence against men with impunity, which makes no sense, as nature doesn't follow this rule. Walk up on any other apex predator and start kicking and hitting them and see how you go. By imposing such standards on men, which goes against every primal instinct they have regarding self preservation, eventually a man will strike back. It's his primary survival instinct when confronted with a threat, even one that some may consider only a trivial threat. If women were treated with the same standards they would also soon learn to keep their hands to themselves, preventing countless unnecessary beat-downs. JMO