There never was a good war or a bad peace. ~Ben Franklin
Professor Pinker explores ideas drawn from his book entitled The Better Angels of our Nature: Why Violence has Declined (2011).
About minute 49' in the lecture, Pinker makes the point that reason "allows us to extract ourselves from our parochial vantage points," which makes it harder to denigrate others or dehumanize others just because you're you and someone else isn't. Reason also allows us to see "the futility of cycles of violence", and therefore, to explore possibilities of extracting ourselves from the pointless cycle of violence, such as by viewing it as a problem to be solved, rather than as a contest to be won.