Darwin himself is not responsible, as in Hitler will be held accountable for his atrocities by the Supreme Lord of All.
His precepts though, contributed to Humanism and was the mechanism (or excuse) for evil men.
ditto to Marxism (which again was used)
Let’s say you’re right. You’re not, but let’s say Hitler never would have thought of demonizing one group as the scapegoats for a depressed and anxious people’s problems, despite the technique’s long history as a political tool, if it weren’t for Darwin; and never would have picked the Jews, despite the long history of anti-Semitism in Germany, without evolution to justify it. What does any of that have to do with whether or not the theory is accurate? The Origin of Species is an explanation, not an advice manual, any more than germ theory is a suggestion that people should develop biological weapons.