Certainly violence takes place in all human societies to some degree - tempers flare, or hot blooded fights erupt, people are executed or otherwise punished by the group. But, I think there's a huge difference between that being an accepted part of how the society operates as it is in dominance hierarchies, and something that is largely discouraged, but just happens to take place. Egalitarianism and the peacefulness it tends to foster don't come about because people are "noble savages." These are intentional strategies for using group pressure to keep individuals from violating the norms of the group because those are all key survival strategies.

When (anthropologist Richard) Lee asked one of the elders of the group about this practice (of insulting the meat from a kill), the response he received was the following: ‘When a young man kills much meat, he comes to think of himself as a big man, and he thinks of the rest of us as his inferiors. We can’t accept this. We refuse one who boasts, for someday his pride will make him kill somebody. So we always speak of his meat as worthless. In this way we cool his heart and make him gentle.’

How Hunter-Gatherers Maintained Their Egalitarian Ways