It's funny how you assume that structured can only happen with violence. You're right, an advanced anarchist society would be a real democracy (not a representative democracy like we have today). It would in fact be way more structured than societies today. If a small group of people can't simply enforce rules on all the others, the bodies that make decisions for the group will have to do a lot more work to make sure they are including everyone in the conversation in order to avoid conflict. It would involve a lot more conversation, deliberation and balancing than our current societies.