Using Nazi Germany as an example, how can a civilised society turn on a group of people?

It is hard to justify how a 'civilized' people could turn upon its own citizens in the way that the Germans did during the 1930's and 1940's. It probably could be stated that a group of people that systematically murders over 10 million people just because they are different is not very civilized. At any rate, Germany was a modern industrial and military power in the early part of the Twentieth Century so some may use that to define civilization. Not to excuse the Germans for the atrocity that was the Holocaust, but many factors contributed to the population accepting the racist and nationalist ideology of the Nazis. There was a strong undercurrent of antisemitism in Europe for centuries that made the genocide more likely. This, coupled with the dramatic economic hardships brought on by the Treaty of Versailles made it easier for citizens to accept Adolf Hitler's rhetoric about the Jewish "problem." Another important factor in the German people accepting the imprisonment and murder of Jews was the fact that many were afraid to speak up and confront the Nazis. Speaking against the Nazis could cost Germans their lives as political dissidents were also targets.