How our better angels' wings might be clipped

To support his hypothesis in  The Better Angels of Our Nature that the human race is, in effect, outgrowing war, Steven Pinker amasses considerable cultural evidence that individuals in the developed world, spurred in part by the development of commerce, have grown progressively 1) more interactive -- able to see another's point of view, address her concerns, meet his expectations; 2) more 'mannerly,' i.e. more self-controlled, less gross to others, slower to signal readiness to take violent action or to in fact take that action; 3) more empathetic, able to imagine another's pain, and hence more reluctant to inflict it; and consequently, 4) more moral, in any meaningful sense of the word.

Assuming that this kind of development has in fact taken place, unevenly but unmistakably, it's possible to imagine opposite directions from which this social progress might reverse itself.