It's the culture of hate sox--it's terrifyingly easy to make a people accept such things when you control all the media, all the schools and indeed life and death of your citizenry. Many Germans unfortunately saw Jews as a corrupting influence on their society, and too many powerful people, educators of the youth and politicians, suscribed to it and made it their lives' effort to convince the rest of the society to condone it or look the other way. You can teach a people that black is white, when you can say this in every book and every radio broadcast, and execute those who disagreed with you.