Wallace, who discovered natural selection independently, called it the tendency of varieties to diverge indefinitely.
Prior to Wallace and Darwin it was thought that varieties always reverted to the "mutt" form.
There is nothing in Wallace's or Darwin's writings that adds anything to the practice or literature of selective breeding.
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.