One of the most controversial parts of the movie Expelled: No Intelligence Allowed was the segment where Ben Stein interviewed the history professor Richard Weikart about his book, From Darwin to Hitler: Evolutionary Ethics, Eugenics, and Racism in Germany. Darwinists went apoplectic, deriding Stein and Weikart for daring to sully the good name of Darwin by showing the way that Hitler and German scientists and physicians used evolutionary theory to justify some of their atrocities, such as their campaign to kill the disabled.Once people reject the idea that morality is rooted in an omnipotent, omniscient, perfectly good being the next logical step is to abandon the idea that there's any objective moral standard at all. This leads inevitably to moral arbitrariness and subjectivity, i.e. what's right is whatever feels right to me. Moral subjectivism leads directly to egoism, i.e. the belief that one should put one's own interests ahead of the interests of others, and egoism leads to the ethic of "might makes right".
Some critics even denied that the Nazis believed in Darwinism at all. Weikart challenges his critics to examine the evidence in his fascinating sequel, Hitler's Ethic: The Nazi Pursuit of Evolutionary Progress, which examines the role of Darwinism and evolutionary ethics in Hitler's worldview.
In this work Weikart helps unlock the mystery of Hitler's evil by vividly demonstrating the surprising conclusion that Hitler's immorality flowed from a coherent ethic. Hitler was inspired by evolutionary ethics to pursue the utopian project of biologically improving the human race. Hitler's evolutionary ethic underlay or influenced almost every major feature of Nazi policy: eugenics (i.e., measures to improve human heredity, including compulsory sterilization), euthanasia, racism, population expansion, offensive warfare, and racial extermination.
Hitler's "morality" was completely consistent with his rejection of a belief in a personal God. Hitler was who every atheist would also be if they a) had the power and b) were logically consistent. Thankfully, few of them are both powerful and consistent, but in the 20th century some were. Mao, Stalin, Pol Pot all were atheists who had complete power within their sphere and acted consistently with their naturalistic, materialistic worldview. The consequences were completely predictable.