I'm Just Following It Back To The Source: "Why Are You Going Over This Again?"

All these questions point to the central enigma of the Holocaust, which has variously been interpreted as a premeditated action and as a barbaric improvisation. In our current age of unapologetic racism and resurgent authoritarianism, the mechanics of Hitler’s rise are a particularly pressing matter. For dismantlers of democracy, there is no better exemplar.

Alex Ross

Well, I've been doing what others are doing, though I didn't understand how important doing it was until the rise of Trump.  From this article by Alex Ross in the New Yorker Last April How American Racism Influenced Hitler Scholars are mapping the international precursors of Nazism.  There is this disturbingly familiar paragraph:

. . . To many liberal-minded Germans of the twenties, Hitler was a scary but ludicrous figure who did not seem to represent a serious threat. The Weimar Republic stabilized somewhat in the middle of the decade, and the Nazi share of the vote languished in the low single-digit figures. The economic misery of the late twenties and early thirties provided another opportunity, which Hitler seized. Benjamin Carter Hett deftly summarizes this dismal period in “The Death of Democracy: Hitler’s Rise to Power and the Downfall of the Weimar Republic” (Henry Holt). Conservatives made the gargantuan mistake of seeing Hitler as a useful tool for rousing the populace. They also undermined parliamentary democracy, flouted regional governments, and otherwise set the stage for the Nazi state. The left, meanwhile, was divided against itself. At Stalin’s urging, many Communists viewed the Social Democrats, not the Nazis, as the real enemy—the “social fascists.” The media got caught up in pop-culture distractions; traditional liberal newspapers were losing circulation. Valiant journalists like Konrad Heiden tried to correct the barrage of Nazi propaganda but found the effort futile, because, as Heiden wrote, “the refutation would be heard, perhaps believed, and definitely forgotten again.”

Hett refrains from poking the reader with too many obvious contemporary parallels, but he knew what he was doing when he left the word “German” out of his title. On the book’s final page, he lays his cards on the table: “Thinking about the end of Weimar democracy in this way—as the result of a large protest movement colliding with complex patterns of elite self-interest, in a culture increasingly prone to aggressive mythmaking and irrationality—strips away the exotic and foreign look of swastika banners and goose-stepping Stormtroopers. Suddenly, the whole thing looks close and familiar.” Yes, it does.

As to the question in the title of the piece, he mentions one of America's premier eugenic-racists of the period:

American eugenicists made no secret of their racist objectives, and their views were prevalent enough that F. Scott Fitzgerald featured them in “The Great Gatsby.” (The cloddish Tom Buchanan, having evidently read Lothrop Stoddard’s 1920 tract “The Rising Tide of Color Against White World-Supremacy,” says, “The idea is if we don’t look out the white race will be—will be utterly submerged.”) 

Alex Ross doesn't mention it, but when you look into what Lothrop Stoddard claimed in that piece of crap mentioned, his conception of such things was indisputably Darwinian:

From classic times down to the end "of the fifteenth century, white Europe had confronted only the most martial and enterprising of Asiatics. With such peoples war and trade had alike to be conducted on practically equal terms, and by frontal assault no decisive victory could be won. But, after the great discoveries, the white man could flank his old opponents. Whole new worlds peopled by primitive races were unmasked, where the white man's weapons made victory certain, and whence he could draw stores of wealth to quicken his home life and initiate a progress that would soon place him immeasurably above his once-dreaded assailants. 

And the white man proved worthy of his opportunity. His inherent racial aptitudes had been stimulated by his past. The hard conditions of mediaeval life had disciplined him to adversity and had weeded him by natural selection.

Whenever someone says "natural selection" they are citing Darwinism, whether or not they say the word.  That his racism was securely rooted in Darwinism is also seen in another of Stoddard's racist diatribes,  The Revolt Against Civilization:

Let us now consider the rise of the new biology, which has already exerted so powerful an influence upon our philosophy of life and which promises to affect profoundly the destinies of mankind. Modern biology can be said to date from the publication of Darwin's work on The Origin of Species by Means of Natural Selection, in the year 1859. This epoch-making book was fiercely challenged and was not generally accepted even by the scientific world until the last quarter of the nineteenth century. Its acceptance, however, marked nothing short of a revoloution in the realm of ideas. Darwin established the principle of evolution and showed that evolution proceeded by heredity. A second great step was soon taken by Francis Galton, the founder of the science of "Eugenics" or "Race Betterment." Darwin had centred his attention upon animals. Galton applied Darwin's teaching to man, and went on to break new ground by pointing out not merely the inborn differences between men, but the fact that these differences could be controlled; 

that the human stock could be surely and lastingly improved by increasing the number of individuals endowed with superior qualities and decreasing the number of inferiors. In other words, Galton grasped fully the momentous implications of heredity (which Darwin had not done), and announced clearly that heredity rather than environment was the basic factor in life and the prime lever of human progress. 

As anyone who has read the pieces I've posted on Darwin's relationship to Galton and his eugenics would know, Stoddard's claim that Darwin didn't go there is wrong.  Not only did Galton, himself, attribute his ideas to Darwin, as soon as Darwin heard Galton's first major book on eugenics Hereditary Genius (the perennially ill Darwin said his wife, Emma read it to him),  he wrote to his cousin praising exactly the points that Galton had drawn from On the Origin of Species, and he endorsed it and Galton's earlier two articles in Macmillan's magazine on the topic, repeatedly, in The Descent of Man.  And those were moderate as compared to the even more extreme claims about that which Ernst Haeckel had published even earlier, endorsing the claims of the immutability of superiority and inferiority and the ethnic and racial assignments of those which are what actually fueled the racism of the likes of Stoddard.   I suspect from checking Stoddard's citations that he never read The Descent of Man, like so many of today's Darwin champions, he never mentions that, his most relevant work to the topic.  

If you go the necessary extra step and look at the things that racists like Stoddard, Charles Davenport, etc. cited to support their claims, books and papers such as those by Paul Popenoe, Karl Pearson,  the Darwinian nature of their thinking becomes obvious.  

The article is especially valuable because it shows how much of the earlier scholarship and writing about the Nazi genocides and their motivation were over-simplistic and to the extent they left out information, the claims made about the origins of Nazism and the genocidalism that was AND IS intrinsic to it were off the mark.  I'm just supplying the ultimate origin of the biological theories of the Nazis and virtually all modern racism, whether or not they admit to where they got their ideas.  I think the anti-intellectualism of a lot of the neo-Nazism is so profound that they don't know what the secondary, tertiary and fourth-generation racism they imbibed came from.  

Here's an example of the cross-fertilization of Nazism with American science, technology, industry and politics and law. 

California’s sterilization program directly inspired the Nazi sterilization law of 1934. There are also sinister, if mostly coincidental, similarities between American and German technologies of death. In 1924, the first execution by gas chamber took place, in Nevada. In a history of the American gas chamber, Scott Christianson states that the fumigating agent Zyklon-B, which was licensed to American Cyanamid by the German company I. G. Farben, was considered as a lethal agent but found to be impractical. Zyklon-B was, however, used to disinfect immigrants as they crossed the border at El Paso—a practice that did not go unnoticed by Gerhard Peters, the chemist who supplied a modified version of Zyklon-B to Auschwitz. Later, American gas chambers were outfitted with a chute down which poison pellets were dropped. Earl Liston, the inventor of the device, explained, “Pulling a lever to kill a man is hard work. Pouring acid down a tube is easier on the nerves, more like watering flowers.” Much the same method was introduced at Auschwitz, to relieve stress on S.S. guards.

And this:

When Hitler praised American restrictions on naturalization, he had in mind the Immigration Act of 1924, which imposed national quotas and barred most Asian people altogether. For Nazi observers, this was evidence that America was evolving in the right direction, despite its specious rhetoric about equality. The Immigration Act, too, played a facilitating role in the Holocaust, because the quotas prevented thousands of Jews, including Anne Frank and her family, from reaching America. In 1938, President Roosevelt called for an international conference on the plight of European refugees; this was held in Évian-les-Bains, France, but no substantive change resulted. The German Foreign Office, in a sardonic reply, found it “astounding” that other countries would decry Germany’s treatment of Jews and then decline to admit them.

The Immigration Act of 1924 was the creation of American scientists, lawyers,  propagandists, politicians, etc. most of those I have read cite natural selection or Darwinism, sometimes by name that name, as providing the scientific validation of their claims.  Stoddard, Charles Davenport. Harry Laughlin, all of them based their eugenics ideas in Darwinism.

One of the things I've collected in my research which I haven't used before is a letter from Charles Darwin's son, Leonard to Harry Laughlin 

October 29 [c. 1932]

Dear Dr. Laughlin, It was indeed good of you to send me the excellent photographs of the pedigrees and to tell me that they had attracted a good deal of attention. As to those who made them including yourself, I should have though you would have all cursed the name of Darwin before the job was done! I am very glad to hear from you that you think the [eugenics]congress was a success and my wife and I sincerely wish that we could have had such an opportunity of meeting many old American friends. I suppose the proceedings will be published when I shall enjoy reading them. With very kind regards from us both to Mrs. Laughlin and yourself.

Yours very sincerely,

Leonard Darwin

All of it including the part that flows like a poisonous sewer through American eugenics to the Nazis, had its head waters in On the Origin of Species, specifically Darwin's theory of natural selection, all of it flows from and through Charles Darwin and his closest scientific and personal associates, Francis Galton, his children such as George Darwin, especially Leonard Darwin whose letters to eugenicists such as Laughlin and Davenport, and German eugenicists, many of them with direct contact with Nazis demonstrate that connection and its importance in understanding the Nazi's application of natural selection.  

The comforting lie that the Nazis were some kind of unique aberration and a peculiarly German manifestation of depravity is made especially dangerous with the rise of Trump and other Putin financed and supported neo-fascist and neo-Nazi politicians.  You won't ever fight it back unless  you admit the extent to which they depend on the idea of natural selection and understand that its character is and has always been ideological.