Hitler spoke of fixed kinds “A fox will always be a fox”.
Genetic diversity is good for a population if one understands evolution. Hitler thought that diversity consisted of a dichotomy of “weak” and “strong” and sought to (through government action) eliminate the so-called “weak”.
Creationists cannot seem to escape blatant lies and historic revisionism. From testimony on the stand at Dover to the constant false equivalence of acceptance of a scientific theory with Nazism, Communism, or atheism - complete with accompanying historic revisionism - those that think they are on the side of God cannot seem to help serving the father of lies.
Hitler was an evolutionary pantheist, not a creationist. He believed that in the struggle for existence, the lower and weaker animals and races were bound to die out. As such, Hitler promoted the notion that “the consequence of this racial purity, universally valid in Nature, is not only the sharp outward delimitation of the various races, but their uniform character in themselves. The fox is always a fox, the goose a goose, the tiger a tiger, etc (Mein Kampf).” Thus on the same page, Hitler placed both man and animals under the same natural laws which must be obeyed, “you will never find a fox who in his inner attitude might, for example, show humanitarian tendencies toward geese, as similarly there is no cat with a friendly inclination towards mice.” Thus, Hitler adopted the Haeckelian-Darwinian survival of the fittest scheme with a vengeance, especially with regard to its application to people, “and the struggle is always a means for improving a species’ health and power of resistance and, therefore, a cause of its higher development.” What in the world this has to do with creationism is a figment of the leftist imagination. As such, Hitler professed the idea that gradual natural evolutionary development over time led to a SEPARATION of the species. Nature’s “most patent rule” was preserving the purity of the races in which all living species developed their own “inner segregation.”
By the way, with regard to the foxes being always the same, this is undoubtedly borrowed from Nietzsche who basically said the same thing. Hitler’s second favorite philosopher behind Schopenhauer was Nietzsche. Nietzsche was not completely sold on the biological theory of evolution, but still assumed the Darwinian struggle for existence to be a law of life.