I believe in the concept of original sin. Man is born into sin and cannot free himself. It is more than self-interest. People engage in all manner of evil acts that will likely be discovered and cause all manner of pain and punishment to themselves and others. Some engage in murderous acts and willfully commit suicide in the process. The wholesale gassing of Jews in concentration camps falls outside the envelope of human self-interest. Stalin, Pol Pot, Mao and Saddam Hussein engaged in a level of evil far beyond such explanations.
The term "self-interest" simply does not cover the depravity of human conduct.
Hitler recognized that his own self-interests would be furthered by getting the public to unite behind him against a "common enemy". Individual people who were involved in his "final solution" believed that going along with Hitler's plans was in their self-interest because it meant they would be promoted rather than shot.
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