I never really understood why people would intentionally try and hurt the ones they care for. Whether physically, emotionally or otherwise. You're supposed to trust and appreciate those you care for. If your SO somehow makes your emotions volatile, then that's not love, and you should avoid that person and move on.
On the flip side though, women are adults too. If they are threatening or inflicting violence, then IMHO men should do what is necessary in self-defense to protect themselves.