From Philip Giurlando’s review of Mein Kampf:
This sad historical episode reveals an important point: that any moral system that rests on equal human dignity cannot flow from the scientific observations of biologists. In other words, universalist moral systems, like liberalism, socialism, or the United Nation Declaration of Human Rights (UDHR) rely on assumptions that are not scientific. The idea that all humans have equal worth is a statement of value that is not verifiable according to the standards of science. Rather, it rests on faith, but this does not make it less true. It means that a strictly scientific materialist worldview is insufficient for the belief in universal human equality. One could even assert that human decency is inversely proportionate to the distance that we create between ourselves and the dictates of nature. The natural world indeed operates in a hierarchical, predatory, and ruthless fashion that ensures the survival and reproduction of the strongest. Hitler not only recognized this, he celebrated and derived his morality from it, as did eugenicists. Universal moral systems like the ones mentioned above can accurately be characterized as attempts to use human agency to overcome these ruthless processes of the natural world. Therefore, attempts to derive moral systems from nature, or to ascribe some transcendental moral agency to the earth, should be taken with a grain of salt.