I think the "everyone almost knows someone personally" thing _really_ depends on patterns of settlement. If the population is very segregated in terms of wheth

I think the "everyone almost knows someone personally" thing _really_ depends on patterns of settlement. If the population is very segregated in terms of whether they live, work, etc (as was the case in Poland), that may well not work. Combined with visibly different modes of dress, different customs, different religion, and different language, the whole "the other" thing just wasn't a hard sell. I agree with your point that mass murder by the millions requires something rather special, not least a combination of (1) feeling that you are not killing people and (2) industriousness that is fairly rare. Plenty of people in Europe in the 30s thought that Jews were worth killing if it wasn't too much work, but weren't quite going out of their way to do it the way the Nazis ended up doing.