Violence is damn near instinctive, probably even biological.
This is true, but there is a clear distinction between cultural tolerance of violence, and it being culturally unacceptable.
After all, in many cultures, adult men are still marrying child brides, but our culture doesn't accept this.
Most people are able to overcome the 'natural instincts' to go around trying to have sex with anything that moves, defecate wherever they like, and grab hold of anything that takes their fancy. Violence against each other can go the same way, without too much difficulty, as far as I am concerned. Those who really cannot keep themselves form lashing out should really be locked away, either in prison, or in a psychiatric institution, depending on whether a judge deems them 'mad or bad'.