White supremacists would like to live in a genetically pure country. They can’t tolerate non-aryan blood. But such a country probably wouldn’t serve them well. Animal breeders know that mixed race animals do better than pure-breds. Race horses may be beautiful, graceful, and fast, but they are more likely than other horses to break down. Mongrel dogs tend to be healthier and live longer than pure-breds. The same is true of cattle and chickens. The offspring of marriages between closely related humans are typically impaired compared to offspring of nonrelatives.
During the past 20 years, African Americans, Hispanics, Muslims, and Asians have won Nobel Prizes, Pulitzer Prizes, most valuable player awards, tennis championships, Olympic gold medals, literary prizes, Grammys, Emmys, and Oscars. Does anyone seriously think that anyone from the Charlottesville gang of Nazi saluting chanters and Confederate flag-wavers is supreme over any of those people? Or, for that matter, supreme over anything other than a pile of rocks?