Kids shouldn’t really be violent, both in their childhood and throughout the rest of their lives.

Yeah but leave them alone and one will hit the other. You need adult supervision to stop it all going Lord of the Flies.

If you leave kids alone they also “play doctor”. What’s natural is a poor indicator for what’s a good idea (that said, it’s generally agreed that kids playing doctor is generally a healthy activity — the same is decidedly not true for hitting each other, or other forms of violence).