I'll admit it. I've hit people twice in my life span. Am I proud of that? No. Would I have -not- hit the people I did if I could change the past? Not necessarily. Both were male and only one of them was I in a relationship with. I was engaged to this man for nearly two years, during which time all manner of one sided abuse (on his part, to me) occurred. After having him scream in my face during an argument where I kept quietly and politely trying to interject a comment and him shouting me down, I slapped him.
People will put up with all manner of abuse for all kinds of reasons. For me at least, I just wasn't willing to see what was in front of my face, and accept that it was abuse. A male friend of mine put up with abuse from his wife for a long time, in order that he could stay involved with his child. Sadly, when he finally did put things in motion to divorce her, she took their child and moved clear across the country.
Another friend of mine made a comment about how their leg hurt, upon being asked why, they mentioned that their significant other had hit them, but it "wasn't like it was actually abuse". Myself and other friends all tried to politely suggest that this wasn't acceptable behavior. After making our point in as non-abrasive a manner as possible, we let it be. I still try and watch out for my friend, but telling them to break up with their partner constantly just wouldn't work. Abuse happens to men as well as women and it's sad.