Germany's eugenic sterilization law, which went into effect on January 1, 1934, is no hasty improvisation of the Nazi regime. It has been taking shape gradually during many years, in the discussions of eugenicists. From one point of view, it is merely an accident that it happened to be the Hitler administration which was ready to put into effect the recommendations of specialists.
But Hitler himself - though a bachelor - has long been a convinced advocate of race betterment through eugenic measures. Probably his earlier thinking was colored by Nietzsche, but he studied the subject more thoroughly during his years in prison, following the abortive revolutionary movement of 1923. Here, it is said, he came into possession of the two-volume text on heredity and eugenics, by E. Baur, E. Fischer, and F. Lenz, which is the best-known statement of eugenics in the German language, and evidently studied it to good purpose. In his book, Mein Kampf, most of which was written during these prison years, and which outlines most of the policies since adopted by the Nazis as a political party, he bases his hopes of national regeneration solidly on the application of biological principles to human society.
Paul Popenoe argues the opposite:
O.K. But I don't see how that opposes or gainsays anything I wrote about Nazi race theory.
Your quote suggests that Hitler was concerned with "racial hygene". I don't see how any of it relates particularly to evolutionary theory generally or darwinian evolution particularly.
In fact subsequent advances in evolutionary theory -- particularly the reconciliation of Mendelian genetics with classical darwinian selection in the "neo-darwinian synthesis" -- seriously undermined eugenics by showing that it's assumptions about heredity were simplistic and therefore it's program unrealistic.