Actually, Darwin's works were on the list of banned books in Nazi Germany. Copies of Darwin were all burned. This is because they were not using evolutionary concepts. They were using crap fake science and real science was a threat to that. Their ideas about breeding superior people weren't even based on evolution--it was based on artificial selection, the basis for animal husbandry for millennia--the artificial culling of those animals with undesirable traits and the preferential breeding of animals with desirable traits, with desirability determined by the whim of the breeder. By definition, evolution relies on natural, not unnatural, selection, to occur. Survival of the fittest makes no judgments about what is fit and what is not fit. It's not the strongest, fastest, smartest, biggest, tallest, blondest, or bloodthirstiest. It's the one that fits best to the ever changing circumstances. So that's a good counter to creationists who make allegations about Darwin and Naziism.

The other answer in this thread provides some information, but it isn't substantiated, shows no source and lacks completeness. I cannot lay claim to knowledge of "On the Origin of Species" being banned or burned in Nazi Germany, nor can I speak towards how well Darwin's theories as they were presented in his writing were known or accepted by the academic or political leaders of Germany at that time. Darwin in and of himself isn't really the issue with the Nazi ideals of racial purity. These spring from a study of humanity which attempted to bring the aspects of natural selection into a sociological sphere-essentially, the idea that one race is superior to another on the basis of genetics or breeding.

"All these views were bundled together into the smart new science of eugenics, which may be simply defined as the scientific cultivation of superior beings." (Bryson 363) In 1920's America, "(i)t led to the sinister belief that procreation should somehow be regulated and directed....Eugenics was used to justify enforced deportations, the introduction of restrictive covenants on where people could live, the suspension of civil liberties, and the involuntary sterilization of tens of thousands of innocent people." (Bryson ibid) That should begin to sound a bit familiar in context to the National Socialist movement in Germany, yes? Mr Bryson goes on to indicate "In the 1930's Laughlin (head of the Eugenics Records Office)...began to establish warm relations with Germany's newly emergent Nazis, some of whom came to Cold Spring Harbor (where the ERO was located) to study American methods and findings." (Bryson 369)

In summation- the Nazi ideology of racial superiority was based in eugenics, which was lifted from a wishful thinking interpretation of the theory of natural selection in a ideological movement known as "Social Darwinism" - "the theory that persons, groups, and races are subject to the same laws of natural selection as Charles Darwin had perceived in plants and animals in nature. According to the theory, which was popular in the late 19th and early 20th centuries, the weak were diminished and their cultures delimited, while the strong grew in power and in cultural influence over the weak. Social Darwinists held that the life of humans in society was a struggle for existence ruled by 'survival of the fittest,' a phrase proposed by the British philosopher and scientist Herbert Spencer. Encyclopaedia Britannica

So the notion that the Nazi's tied their policies into evolution does not begin to reach a complete understanding of the subject at hand, and any group that is willing to foist a single reason for the causation of such a complex event is grasping at straws.

Source: Bryson, Bill One Summer America 1927 Doubleday Books, 2013