"Decent Nazis"
The Nazis were one of the worst and most violent groups of people in history, yet Frankl mentioned that there were "decent Nazis." In other words, there were Nazis who were good people placed in a bad situation.
"Indecent" Prisoners
Prisoners in concentration camps who were treated terribly and dehumanized subjected their fellow prisoners to similarly awful treatment. These men were called the kapo, who acted as substitutes for the SS guards.
Humanity
Even though he experiences some of the worst and most dehumanizing treatment ever done to man, Frankl left the concentration camps with a renewed sense in the goodness of humanity -- not that humanity was awful.
Finding Meaning in Spite of Immense Suffering?
Despite his awful circumstances, Frankl was able to find meaning in his life. Virtually all of the concentration camp prisoners, Frankl says, simply endured their experience in the concentration camps and found no meaning whatsoever in their life. Frankl was able to look back on his life, particularly his time with his wife, and find meaning to keep living.
Growth Through Immense Suffering
Most prisoners were totally broken by their experience in the Holocaust. Frankl, on the other hand, was not. Even though he suffered tremendously, Frankl claims that he grew as a person because of his experiences in the concentration camps.