How does the idea that the victim somehow somehow regarded as “evil” affect all atrocities and mass killing?

The anti-Semitism we see in Schindler's list is an extension of Hitler's views on the Jewish people. Hate and bigotry are not logical concepts, so they are open to manipulation. Hitler was able to manipulate a fairy large group of people into believing the victim to be enemies of the "fatherland". War and economic depression make fertile ground for extreme populist politics. Hate is an easy thing to sell, especially when people, like many Germans at the time, feel they have been the target of unfair treatment by the world. Hitler was able to channel post-ww1 anxiety and pervert it into genocide of Jews.