Rubbish. People were believing that certain races were inferior long before Hitler, or Darwin.
It is wrong to blame Darwin or his theory for Hitler, but it is also wrong not to acknowledge the intellectual origins of Hitler's policies, or those of Marx. That's like claiming that the lone Muslim who shot a bunch of Jewish women was just a "confused loner," rather than someone acting on the basis of ideology.
Darwin's ideas of natural selection were influenced by his knowledge of artificial selection. It's an obvious and predictable step to reverse his thought process, and propose that if natural selection "improves the breed," artificial selection will do it faster, and therefore we should intervene actively. Anyone who looks at the astounding diversity of domestic dogs can see how rapidly artificial selection works.