Did the Nazis understand Darwin or did they distort his ideas for propaganda purposes?

The Nazis twisted Darwin's theory of natural selection. They used it to portray human life as a struggle between various races for control of the earth's resources. This shallow reading of Darwin became a pseudo-justification for violence and brutality towards 'the enemies of the state'. Hitler said openly that pity and compassion were only to be shown to fellow Aryans and never to other races. This is the ideological basis of Auschwitz. However, this is not the fault of Darwin, this is what Churchill called 'perverted science', the Nazis 'forgot' that we also have free will and the ability to make choices about how we treat other people.