In the above video Pinker touches on how our understanding of democracies as peaceful has changed. Scholars now believe it may be the capitalism that really prevents war-making (see China). A recent review challenged Pinker on similar territory:

Since democratic nations reportedly don’t go to war with each other, they are said to be more peaceful than (say) military dictatorships. Pinker neglects to inform us, however, that they can form coalitions of the willing so as to export democracy through warfare, and there is negligible mention of the scale of resources absorbed by military activities in ‘peace loving’ democracies. The role powerful democratic nations play in supporting repressive regimes (through arms sales and foreign policy) is similarly obscured via an emphasis on “gentle commerce” (p.165 et al). According to Pinker, a “free market puts a premium on empathy” (p.77) because it encourages trading partners to see things through one another’s eyes, thus curtailing their violent impulses.

Previous videos of Steven Pinker, author of The Better Angels of Our Nature: Why Violence Has Declined, here, here, here, and here. “Ask Anything” archive here.