Kicking a rooster (or any chicken for that matter) is a BAD idea. Please don't do that again, no matter how big the urge. They have such fragile bones, you could cause it serious injury. Even if they are being completely obnoxious there are better ways to "punish" them, like picking them up and carrying them around a bit. They hate that. Or put your hand on his back and hold him down firmly for a minute. I know roosters can be difficult, but kicking him is not going to resolve the issue. Rather separate them and let him cool his heels. Roosters will fight and compete, it's their nature. Especially in a situation like yours. Your roo is used to having the ladies to himself and now you've come and upset the apple cart. He's going to fight to keep his ladies. When roosters grow up together they usually learn to live together, but when you introduce a new roo to the flock there will be conflict. If there's enough hens for them all they may eventually sort it out, but if they won't, keep them in separate pens, each with their own hens, or decide which one you want to keep and rehome the other.
