It's finally happened to me.
I was baby-sitting with my mom. She was on the phone outside and I was watching the 2 boys, 7 and 12 inside. They were getting into it. The 7 year old was kicking and hitting the other one, who was just trying to ignore it because the older one said something the young one didn't like.
So once I got him away, I told him that just because he said something doesn't mean you have to go hitting him.
It was then that I heard an echo in my head, the voice of my mom telling me the same thing when I was young and in fights with my brothers (quite often, actually).