Jared Diamond looks at tribal justice in The New Yorker:
Though we might wonder how Daniel’s society came to revel in killing, ethnographic studies of traditional human societies lying largely outside the control of state government have shown that war, murder, and demonization of neighbors have been the norm. Modern state societies rate as exceptional by the standards of human history, because we instead grow up learning a universal code of morality that is constantly hammered into us: promulgated every week in our churches and codified in our laws. But the differences between the norms of states and of Handa clan society are not actually so sharp. In times of war, even modern state societies quickly turn the enemy into a dehumanized figure of hatred, only to enjoin us to stop hating again as soon as a peace treaty is signed. Such contradictions confuse us deeply. Neither pacific ideals nor wartime hatreds, once acquired, are easily jettisoned. It’s no wonder that many soldiers who kill suffer post-traumatic stress disorder. When they come home, far from boasting about killing, as a Nipa tribesman would, they have nightmares and never talk about it at all, unless to other veterans.
Then, too, for Americans old enough to recall our hatred of Japan after Pearl Harbor, Daniel’s intense hatred of the Ombals may not seem so remote. After Pearl Harbor, hundreds of thousands of American men volunteered to kill and did kill hundreds of thousands of Japanese, often in face-to-face combat, by brutal methods that included bayonets and flamethrowers. Soldiers who killed Japanese in particularly large numbers or with notable bravery were publicly decorated with medals, and those who died in combat were posthumously remembered as heroes. Meanwhile, even among Americans who had never seen a live Japanese soldier or the dead body of an American relative killed by the Japanese, intense hatred and fear of Japanese became widespread. Traditional New Guineans, by contrast, have from childhood onward often seen warriors going out and coming back from fighting; they have seen the bodies of relatives killed by the enemy, listened to stories of killing, heard fighting talked about as the highest ideal, and witnessed successful warriors talking proudly about their killings and being praised for them. If New Guineans end up feeling unconflicted about killing the enemy, it’s because they have had no contrary message to unlearn.