"And when they came for me, there was no one left to speak out for me." —Martin Niemoeller

I think that quote speaks a little about the worst enemies within us, in purely clinical terms, that what's in the best interest of those with whom you don't necessarily explicitly associate yourself may also be in your own best interest.

The thing to keep in mind about the Jewish Holocaust is that it wasn't particularly unusual. It was unusual mostly in its location: it was rare to carry out such large scale atrocities ''in Europe''. Exterminations had been carried out by various states upon people in every other part of the world. Some were absolute, and entire races were exterminated. Hitler had great admiration for how the United States dealt with its native population. Sweden exterminated slaughtered whole groups in Africa. The list is not as short as we'd like it to be.

An interesting (and depressing) book: Exterminate All the Brutes by Sven Lindqvist

What I took from this book is that the enemy that is the holocaust situation is within us. The Jewish Holocaust was (unfortunately) not an outlier, but rather was/is in our culture or genes or humanity (I'm not sure I know which, although I tend towards the genetics).