Long post/story but it's relevant.
My mom was a social worker for 4-5 years with an organization back when we lived in Scotland. The place where she worked was specifically a shelter and a social resource for abused women of minority origin. Seeing as how my family is Indian, my Mom fit right in.
Due to how poor we were our family couldn't afford childcare so, after school, I would usually end up at either my Mom or my Dad's workplace. My dad worked for Edinburgh university as a programmer so his workplace was pretty normal but my Mom . . . well, her office was a real eye-opener. I never really realized it until I grew up but I got a real education there. Abused women used to come in with their children literally (and I do mean literally, like kneeling on the ground) begging to be taken so they could be spared another beating from their husband. Some of them used to be bruised or have violence marks, sometimes their kids would be bruised. I remember one lady who was abused so harshly she developed 2 or 3 other "personalities" to help her cope with it-one she had for her kids, one she had for her husband and one she used to talk to other people. While she was working there, my Mom got her 3rd or 4th Bachelor's degree in Social Work, specifically focused on domestic violence issues.
Now, you may be asking how all this is relevant and here's how: throughout all this, my Mom was herself the victim of domestic abuse. None of it was anywhere near as violent, brutal or damaging as the people she helped but it happened. Like I said, my family was poor and we had a rough time in Scotland. Being Indian in Scotland in the early to mid-90's was bad times. We got harassed, racial slurs were frequently directed our way, I used to get beaten up, spat on or have my clothes torn at school every week or two at school. All of this put a lot of stress on my parents relationship and they used to argue every 2-3 months. On some occasions, those arguments would result in my Dad hitting me or my Mom. It was very wrong and he should never have done it but it happened. Over all the years that we were there, I remember either me or my Mom getting hit many times each. A few of those times, he either hit me hard enough that I got thrown to the ground (I was around 10-11 years old) or hit me multiple times until I was curled up in a fetal position. My Mom stayed with him through all this.
When this happened and my Mom decided to stay with my Dad, I didn't understand why. How could she stay with someone who was exactly the sort of person that she advocated and worked against? I couldn't understand it. When I talked to her later she told me that she felt that my Dad was not normally a violent person and it was just the stress of our living conditions that made him hit us. I didn't buy it then but, to be perfectly fair to both her and my Dad, since we moved to the US and both of my parents started getting paid more than peanuts, my Dad has never hit either of us. He has also apologized profusely to both of us and expressed genuine remorse for what he did. After seeing everything at my Mom's workplace and at home, I can understand both sides of this issue.
Sometimes people, even the most informed, rational and smart people will not do rational things when it comes to their relationships. Sometimes, when they stick with the relationship it can work but it requires a very narrow set of circumstances and a very good read on your partner.
For me personally, I could never abuse anyone in a relationship. After getting hit by my Dad and seeing my Mom get hit by him I have a very good appreciation for what abuse can do in a relationship. I know that, compared to some, my Mom and I got off lightly so to speak. Just the fact that I still have a loving family is kind of a miracle and it's not usual. However, after seeing my Mom crying and knowing how she felt when she got hit, I could never hit a woman that I'm in a relationship with. After seeing and hearing my Dad crying and wracked with guilt immediately afterwards, I would never resort to violence that I know won't ultimately solve anything or make me feel better.
More than that though, I am always afraid that I have the capacity for violence within me. Maybe it's irrational, but in relationships I'm always watching myself to make sure that I don't get too angry or too upset. Seeing my Dad hit my Mom has made me afraid that I might do the same. It's never happened yet and, rationally speaking, it won't happen. It still doesn't change anything. The only thing that ever worries me when I'm in a relationship is the possibility that, if I ever get into a fight with my girlfriend, I might hit her. I'm really, really paranoid about it but I've never touched any of girlfriends in a violent manner. There was one time that I got into an argument and when she yelled at me and turned to walk away I reached out and grabbed her arm somewhat hard. I can never adequately describe the shame that I felt right after that moment.
I won't stand any violence on my part in a relationship. I've been in exactly one relationship where my girlfriend hit me. I gave her one freebie before I walked.