When is it okay for a man to hit a woman?

Well at school me and my freinds talked about it, and other joking around and saying he put a new meaning to "Take you down" and that he was lucky she didn't headbutt him, (forehead joke) that it was probly the first thing that came to him to do out of anger. I mean i've seen and spoke with chris (for all of 5 seconds) and even though he did have kind of a stank attitude, I didn't expect him to hit her or anythings ._.