Throughout history, ethnic groups have suffered mass campaigns of genocidal slaughter. Perhaps the most horrific of these campaigns was the Jewish Holocaust, in which Adolf Hitler’s Nazi regime murdered an estimated 6 million Jews, two-thirds of the total in Europe, and up to 90 percent of the Gypsies in Germany and Austria. In the late 1970s, Cambodian communist dictator Pol Pot evoked comparisons to Hitler when he had more than 1 million Buddhist, educated, and minority Cambodians massacred. Both Hitler and Pol Pot mistakenly believed that eliminating entire ethnic groups would produce greater societies.

Incredibly, many of those responsible for these deaths wholeheartedly embrace the idea of genocide and openly justified their atrocities. As Adolf Eichmann, a Nazi secret police colonel executed for sending Jews to their deaths, coldly declared: “Jewry is now suffering a fate which, though hard, is more than...