What might explain why Darwin's evolutionary theories were (and continue to be) so vehemently rejected by and morally offensive to so many people?

What might explain why Darwin's evolutionary theories were (and continue to be) so vehemently rejected by and morally offensive to so many people? Did Social Darwinism and eugenics represent a "distortion" of Darwin's theses or were they logical conclusions to be drawn from Darwin's ideas?

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