Pithy version: Hitting kids to show them that hitting other kids is wrong?

Less pithy version: The message you send by beating kids, is that violence is wrong unless you're big and strong enough and have enough authority that nobody can stop you. This is not a good way to get kids to be less violent, it just teaches them to be more calculated in their violence.

another take: some people are emotionally “dumb” and have a really hard time feeling empathy for others. This is just another way to force the bully to be in someone else’s shoes…literally.