" In some important aspects the Nazi genocide was not unique. In numbers killed, Hitler was surpassed by Stalin and by Mao. In proportion of the population killed, he was surpassed by Pol Pot. But, in other ways, there was a unique moral horror to what the Nazis did. There was an intensity of positive hatred in those who planned the genocide, "

― Jonathan Glover , Humanity: A Moral History of the Twentieth Century