Comparing the Inquisition and the Crusades to 'natural selection' or 'a master race' is comparing apples to oranges, however. The Crusades were not really to further Christianity but were to bolster the prestige and power of corrupt popes and/or monarchs. The Inquisition was not all that much different--it was largely instigated to strike fear into the hearts of people and keep the power in the hands of those same corrupt popes and/or monarchs. Such corrupt popes and monarchs were at times thoroughly dishonest and calculating, but they weren't crazy. Their rationale in no way resembled Christian teachings but were a grievous corruption of Christian teachings.
Hitler's crazy notions of course were to bolster his own power and authority but were based on irrational criteria that included a kind of eugenics that was a corruption of Darwin's basic theory of natural selection.
Hitler's criteria for his policies:
International relations are an endless and merciless inter-racial struggle for domination.
His "racial" division of mankind is a hierarchy, with the "Aryan race" (the Germans) as the master race at the top, followed by the "Nordic" peoples of northern Europe, followed by other nations and races, with the Slav peoples of Eastern Europe at the bottom, and the jews totally outside the hierarchy as a demonic arch-enemy of the Germans.
As the master race, the Germans are entitled to, and must, expand their territory by merciless force, and enslave "Lower races".
Particularly, the Germans should occupy the vast lands of Eastern Europe, enslave its peoples, exploit its endless natural and agricultural resources, and fill it with Germans.
To be as strong as possible, the Germans must strictly keep their "Racial purity", and be led by a Fuhrer (leader) of total authority - Adolf Hitler.
The jews, the "Arch enemy", should be eliminated.
Hitler also believed that Communism, and particularly the Soviet Union, are in Jewish control. This doubled his motivation to attack Russia.
Finally, with Eastern Europe's resources in their hands and with the jews out of the way, The 3rd Reich (Hitler referred to Nazi Germany as the 3rd German Empire in history) will be able to defeat all other nations and dominate the entire world "For at least a thousand years".
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I don't know if Hitler read Darwin but Darwin was being widely read and discussed throughout the free world in the 1930s and 40s. I do see a correlation between the two theories with Hitler's theory being a grievous corruption of Darwin's teachings.