This DailyKos post, Big Mike and the Paper Hanger, discusses the flaws in Francis Galton's theory of Eugenics, that stellar example of bad science from the 19th Century that led to the Nazi final solution and still holds sway with many birthers and educational testers.* Short version of the Kos thesis: genetic diversity is good, and non-diversity results in the death of species. Breeds such as the over-refined Big Mike banana discussed in the post, a "larger, sweeter, tougher banana that was sold before the 1950s," is "nearly extinct after a fungal disease struck banana plantations around the world... Because all the Gros Michael were the same, they were all susceptible to the same disease. " By extension, your Nazi superman (here's where the paper hanger comes in) would have been a similarly vulnerable hothouse strain.
Not discussed in the article is the point that seems to me most glaringly wrong about Eugenics: the huge jump in logic it takes from conceiving an effort to weed out traits in a small portion of the population (inheritable disease) to weeding out the majority of humans on earth (non-WASPs). It should have been obvious from the start that Eugenics was scientific hokum to justify its practitioners' racial prejudices. The hero of the Kos post is Francis Galton's older half-cousin, Charles Darwin, who "considered most people to have more or less the same level of intelligence" and "regarded accomplishment as a measure of opportunity and hard work." Races did not exist to Darwin, according to the post, "except as a convenient way to group individuals that carried some common traits. Evolution could not act against race, because race was no more than a construct, a fiction. Only individuals existed for the purposes of selection."