J.M.
One of my hard and fast rules is that no one is allowed to have "angry feet or angry hands" in my house. The punishment for physical aggression is one spank on the rear end. I personally don't consider that "aggression" on my part because my intent is never to cause harm - it is a disciplinary tactic. And it is a very effective one.
I have a friend with a four year old son. He is extremely aggressive and will even slap and kick at his own mother. His mother doesn't agree with corporal punishment. She is the sweetest, kindest, most generous person I know. They don't watch anything violent and she was just beside herself trying to figure out how her son "learned" to be so aggressive. (I think it's a personality trait. Some children are just naturally more aggressive - and it's up to the adults to direct the aggression into socially acceptable actions.) Even knowing that corporal punishment is one of the disciplinary tools I am willing to employ, she still wanted me to watch her son one day per week. I made it VERY clear that my rules and punishments would apply to her son and she reluctantly agreed. In the first week, her son physically attacked my son when my son refused to give him a toy he was playing with. He got a spank on the bottom. About six weeks later he kicked my neighbor's two year old and got one spank. That was the end of his bullying in my house. Over the next six months, he got kicked out of preschool because of his aggression but in my house he kept his hands and feet to himself. (This does not mean he was a perfect angel. He and my son would still argue and bicker, but they darn sure kept their hands to themselves.) I am VERY consistent - and spanking is most definitely NOT the punishment for every offense. For name calling or "angry words" - the punishment is a time out to the bedroom. For other types of misbehavior, the punishment might be taking away privileges, etc. But physical aggression earns a spank every single time it happens, and because I am so consistent with this I don't have a problem with physical aggression in my house.