I think that it's more about children thinking that everyone is equal in having to keep their word. If you make a promise then you're supposed to keep to it. What often disillusions children is that people in positions of authority often make promises, but don't keep them, yet when it goes the other way around those people will coerce everyone else into keeping the promises to them.

It's a naive position of someone with a nice upbringing without bullies to show that under the veneer there is suppressed brutality of those willing to use violence.