1.Children cannot defend themselves and are portrayed and thought of as "innocent beings". Some people will try very hard to always do right by them, whereas other people will prey on their innocence and weakness. Childhood experiences make you what you are today.
2. From the beginning of time women have been categorized as the weak and unintelligent. We have been merely maids and child-bearers. As the times changed we began to be seen equal but still weak. Most men are stronger than most women, as their bodies are built to do more strenuous labors, therefor it is not so much unfair but unethical to harm a woman. In my opinion, men that harm women are insecure, weak (have to fight females because they are too weak to fight males), and mentally sick. But, if a woman takes a man's place and hits first than you should do what you have to, to disarm her or simply make her stop. That is in no way saying that you should beat her constantly because you just feel like it or are mad at someone.
I myself will not harm anyone unless a situation arrives where there is no way out with my life.