Your complaining about the advice to that question. I actually wanted to know what you thought they should do.
I've been through that age of parenting. That's the age where those discussions should start. If you don't have them, then the child will fill in the gaps best they can. Their conclusions can vary wildly from what we would call reasonable, when that happens.
I taught them that they were allowed to block and to push the other child away, if they didn't stop. They were then expected to immediately get an adult involved. Punching and kicking weren't allowed.