How does Frankl describe the character of the prisoners and the guards?

Frankl writes that it is an oversimplification to believe "that these men were angels and those were devils." While among the guards there were "some sadists," Frankl claims that "the feelings of the majority of the guards had been dulled" through years of exposure to violence, and there were some guards who "took pity on us." Of course, he also details the way in which some of the prisoners, the Capos, were cruel as well. From all of this, he writes, "We may learn that there are two races of men in this world, but only these two -- the 'race' of decent man and the 'race' of the indecent man."