I guess things are not as black and white. Humans tend to be cooperative and many will help a complete stranger that is in a bad situation without potential rewards for themselves. In my opinion this is the key to the success of humans in this world. But obviously humans are also capable of being violent and brutal.
So the key seems to be to build societies that work well for humans and leverage positive cooperation, for example free market capitalism.
kids will hit you in the face until you teach them not to. I personally have always depended on the kindness of strangers. There is a documentary about rats and when the rats are well fed and there is an abundance they are social and cooperative, when there is not they kill and eat each other until there is only one, like the highlander.