it's not a good thing.
But I will say when you're trained to throw punches and be aggressive since the age of 8-10 or whatever, and do that day in & day out your entire life, it's not as easy to simply press the "off" button. Sometimes, I'd imagine, a boxer's instinct when angry is to strike or get physical since it's in his nature and has been programmed to do so his entire life. Obviously some guys are better than others and don't have the problem, but for certain people, maybe specific personality types, it's not that easy.
But if we are going to make a list of boxer's who have hit a women, the list would be MASSIVE.