Humans don't behave violently in conditions of overcrowding or scarcity. (Look at actual crowds and food lines.)
Human violence happens almost exclusively between adolescent males competing for dominance with males from outside groups, and in social situations arranged on that model.
The stress that a person needs to discharge doesn't come mainly from a drive to violence; it comes from a drive to act physically for well-being and to get necessary things for survival. It needs release through physical exercise or else causes worry, depression, and other nervous disorders. Why people don't exercise, how social norms constrain them to sedentary behavior, that I don't know yet.
[I wrote the above as a comment on a post about violence at the blog How to Save the World.]