Well, since everyone wants to argue about who does what, this link seems to contraindicate the view that men are brutes and women are angelic delicate little flowers.
http://www.domesticviolenceresearch.org/pages/12_page_findings.htm
The methodology for collecting data in the previous link
http://www.victimsofcrime.org/library/crime-information-and-statistics/intimate-partner-violence
is clearly flawed as it is based on criminal statistics, and will thus carry all of the biases associated with the law and it's applications. Besides the old fashioned ideas, one of the reasons for this fallacy is the consequences of these violent acts. Men tend to be larger, I am used to being 20% taller than the women in my life, and 50% to 70% heavier, then there are the general skeletal efficiencies. (did you know that for the same weight class in powerlifting men are expected to be able to lift as much as 40% more?) Men are generally capable of inflicting more serious injuries with the same amount of effort. That's not really a good moral standard though, sounds like all the murderers in prison with Dahmer saying "Yeah, but I never tried to eat them."
I saw a sign once that said "Except for ending slavery, oppression, and genocide, war has never solved anything." It seems that despite what everyone's mothers and teachers told them, sometimes violence is the answer. We all have it in our toolbox, the question is about when we feel it is appropriate. Like any tool, using it has consequences, if we are rational we are only going to use it when the benefit is of more value than the consequences. Part of the implicit deal with the soldiers who ended slavery, oppression, and genocide, was that they would not be facing the normal consequences for their actions. Nobody would sign up for the military if we told them they would be charged with murder and assault after the fighting was over.
When the consequences are light enough, then yes, people do believe they will get away with it. Practically speaking, women have far more reason to believe they will get away with it. The legal consequences are much less likely, and there is even a high chance that it will be the man who she attacks that will face the legal consequences.
There are other consequences to resorting to violence as well. Men are very familiar with these, though they usually apply when one resorts to violence against someone bigger or stronger. We learn these lessons early on, in the playground, and in sports. (When I played hockey, sometimes I was the consequence for those who resorted to violence, because sometimes 2 minutes or 5 just wasn't enough.)
There was also a belief back then that it was wrong to hit girls, for any reason. This meant that the only girls who would learn of these consequences were the ones who got into fights with other girls. Now how many of those who think it's okay to hit men think it is also okay to hit women?
Yeah, I do believe that the reason people hit their partner is because they believe they will get away with it. In the case of women, they are unlikely to face the legal consequences, and do not believe that the men will hit back. In the case of men, they do not believe that their wife will call the police, and are not worried about being hit back.
Paraphrasing Robert E Howard (or was it Robert Jordan?), barbarians tend to have far better manners than civilized men, because they know they could find an axe embedded in their skull. (Now why does Chrome think that axe is a typo?)
UO is absolutely right about the posts here. I have never seen a man post about hitting his wife, regardless of how horrified he already was, without "not cool bro" responses being the kindest and most understanding things said. I have also seen a lot of posts over the years by women, often bragging about it, and it used to be 50/50, and depend on who got respond first, whether it would condemn the violence in a gentle manner, or be filled with a chorus of "You go girl!" Thankfully that last reaction appears to have been phased out.