Pretty facile conclusion. As js1188 notes, that line heads well past Darwin. The idea of breeding humans as one would livestock goes back to the Spartans, and filtered through European aristocracy for a very long time. With so many more obvious antecedents, the singular choice of Darwin's reference to artificial selection in his analogy to natural selection as the casus belli of Nazi criminality is fairly obvious -- demonization of the theory of evolution in lieu of scientific rebuttal.
Indeed, the Nazi expropriation of eugenic postulates appears more directly similar to the Lamarckian view of evolution as independent lineages progressing up a ladder.
And there is little doubt that eugenics' champion, Francis Galton, genuinely disagreed with Darwin concerning the mechanism of evolutionary change. Galton held that the small, incremental steps of natural selection would be subverted by "regression to the mean," a belief, in short, that evolution must proceed by discontinuous steps, or saltations, that he called "transiliencies." Pretty clearly a throwback to Huxley and Lyell.
Your straight line, RegulatorCountry, has some oddly curvilinear qualities.
"Selective breeding of human beings was suggested at least as far back as Plato, but the modern field was first formulated by Sir Francis Galton in 1865, drawing on the recent work of his cousin, Charles Darwin. From its inception, eugenics (derived from the Greek "well born" or "good breeding") was supported by prominent thinkers, including Alexander Graham Bell, George Bernard Shaw, and Winston Churchill. Eugenics was an academic discipline at many colleges and universities. Its scientific reputation tumbled in the 1930s, a time when Ernst Rüdin began incorporating eugenic rhetoric into the racial policies of Nazi Germany. During the postwar period both the public and the scientific community largely associated eugenics with Nazi abuses, which included enforced "racial hygiene" and extermination, although a variety of regional and national governments maintained eugenic programs until the 1970s."
http://en.wikipedia.org/wiki/Eugenics
Eugenics has never gone away and never will go away. Support for eugenics is widespread on FR. Just the other day there was a thread celebrating the likelihood that conservatives were having more children than liberals.
On other days there have been threads worrying about Muslims having more children than Christians.