Why did the Germans kill millions of Jews? What drove them to want to exterminate a peaceful and nonthreatening population? Were they appalled by what they were doing?
"Hitler's Willing Executioners," by Daniel Jonah Goldhagen, delivers a brutal and overwhelmingly powerful answer to such questions.
In the 19th century, that [anti-Semitism] merged in Germany with the pseudo-scientific notion that Jews were a "race," so that anti-Semitism became divorced from religion and could be directed with equal intellectual validity at Jews who had converted to Christianity. Since the noxiousness of Jews was, according to that view, intrinsic, assimilated Jews were perceived as particularly dangerous, carrying Jewish corruption deeper into the core of German society.
The German attack on German Jews was the incomprehension, fear and, finally, hatred of the Jew as the "other" who lived next door. Goldhagen cites the massacres of Armenians by Turks and Hutus by Tutsis and vice-versa, among many other gory and shameful examples of internecine slaughter. Nazis knew how to make use of people's inability to recognize the humanity of the "other."