A somewhat minor point in Steven Pinker's The Better Angels of Our Nature is that humor and satire can undermine the propensity to violence, whether by defusing a specific tense situation or taking on national policy.
He gives examples from Shakespeare, Swift, Voltaire, Tom Lehrer, Charlie Chaplin, and the Marx Brothers, including a longish description of a scene from Duck Soup:
...an outlandish production number breaks out in which the Marx Brothers play xylophone on the pickelhauben of the assembled soldiers and then dodge bullets and bombs while their uniforms keep changing, from Civil War soldier to Boy Scout to British palace guard to frontiersman with coonskin cap. War has been likened to dueling, and recall that dueling was eventually laughed into extinction. Warn was now undergoing a similar deflation, perhaps fulfilling Oscar Wilde's prophecy that "as long as war is regarded as wicked, it will always have its fascination. When it is looked upon as vulgar, it will cease to be popular" (p. 248)Later in the book, Pinker sums up an aspect of humor I've always wanted to be able to explain: "Humor works by confronting an audience with an incongruity, which may be resolved by switching to another frame of reference. And in that alternative frame of reference, the butt of the joke occupies a lowly or undignified status" (p. 633).
The current pepper-spraying cop meme running around the interweb is a great example of how humor can help change the frame of reference.
As if the real-time photos and video of the UC Davis incident weren't enough, the doctored images of Lt. John Pike pepper-spraying the Declaration of Independence, baby seal pups, and the Last Supper (among many others) clearly point out how unacceptable his behavior was. And the audience participation nature of the Photoshop meme makes it all the more transformative a moment.
Pinker again: "Humor with a political or moral agenda can stealthily challenge a relational model that is second nature to an audience by forcing them to see that it leads to consequences that the rest of their minds recognize as absurd" (p. 633).
Part 5 of Steven Pinker Week at Daughter Number Three.