Unfortunately, Marg, you're dead on, again. The "right" response very often fails to get the "right" result. Its sad.
I am not proud of it, but when Wee was barely 4, I resorted to "payment in kind" with a group of kids. We were camping and Wee was playing on the playground equipment next to our camper. There was a group of kids there, also, the oldest of which was probably 11 or 12 and another little girl, about Wee's age. This group of kids tried to get Wee to hit the little girl with a plastic baseball bat. Wee instead, turned it on the "leader" of the group, and beat the tar out of him. I moved quickly, but Wee got in several good swings before I got to him and stopped him. His friends were laughing hysterically because he was being severely beaten by a little kid.
For the next several days, this kid taunted Wee from a distance, encouraging a "rematch". I talked to him, I talked to his friends, I talked to the parents, and still, the kis had free run of the campground and it continued.
Finally, one afternoon, Wee was back on the play equipment, and these kids showed up. I was out of view of them, but within earshot, and the "leader" sent another kid for the bat, and told Wee they were going to fight again. When the kid showed up with the bat, I stepped in and grabbed it from him. I held the bat high and told that kid that Wee was a young child with delays and he looked up to older kids to show him right from wrong, and last I knew, fighting with a 4 year old wasn't cool for a kid of any age over 5. I told him if I heard one more word of this rematch, that I would take the bat to him myself.
Unfortunately, that worked.