Man is rational. He engages in predation when it suits him, parasitism when it is possible, cooperation when it is preferable, and flight when it is necessary.
Thankfully, through organizing our efforts into myth, ritual, habit, norm, and law, we can raise the cost of predation and parasitism high enough so that man chooses cooperation or flight more often than parasitism or predation.
Our deprivation of his opportunity for parasitism and predation do not change the nature of man – because man is rational. We simply eliminate those less able to cooperate and produce, and provide disincentives to those that remain, thereby creating an imbalance of incentives and proclivity for cooperation and production.