I have four, one is nearly an adult (in my eyes he is). We negotiate with our children. It isn't always easy, and they hurt each other a lot. When they hurt each other, they can get pretty brutal about it too.
They are not getting that from us as their parents, so I'm not sure where it is coming from. Maybe that is part of the problem with media these days and video games, or maybe they are learning it from their peers or teachers. I'm just not sure. It is a constant battle though.
We ask them to do something, and they do not want to do it? I'll offer to pay. The house can be a disaster from their regular play, and amazingly it will be all picked up and organized in a few short minutes when $5 is the prize for whoever does the most work.
They just need the right incentives to do what we want them to do. That is the same truth behind Human Action and the entire world economy too. The incentive should not be from fear of violence however. Well, even that brings up a gray area. If someone attacks them, they are allowed to defend themselves within reason.
Therefore a violent counter attack is actually a good incentive for people not to use aggression.