It seems the theme of the book list is that sometimes an idea can have very serious consequences even though that might not have been the writer's intention. It's easy to see how the ideas represented in Mein Kampf led to the deaths of millions. It was a hate-filled screed from beginning to end. Even more people were murdered in the name of ideas from books like The Communist Manifesto, Quotations from Chairman Mao, and Das Kapital, even though the books don't advocate gulags, mass murder, and starvation as government policy.

With Darwin, it's not so easy to see why anyone would put his book on the list. However, the full title of Darwin's most famous work was On the Origin of Species by Means of Natural Selection, or The Preservation of Favoured Races in the Struggle for Life.

During the colonial era, quite a few people were oppressed by a misreading of Darwin's writings. The concept of "survival of the fittest" was frequently cited during the colonial era as grounds for exploiting the "lessor races", most likely by people who were seeking rationalizations for their own behavior rather than by anything Darwin himself wrote.

There are some who claim a connection between Darwin and the evolution of genocide, see also here, though that seems a stretch to me. For most of "Origins", Darwin uses the word "race" the same as we use the word "species" or variety (such as discussing the "races" of cabbage on page 15), he also throws in the human race on page 198-299:

But we are far too ignorant to speculate on the relative importance of the several known and unknown laws of variation; and I have here alluded to them only to show that, if we are unable to account for the characteristic differences of our domestic breeds, which nevertheless we generally admit to have arisen through ordinary generation, we ought not to lay too much stress on our ignorance of the precise cause of the slight analogous differences between species. I might have adduced for this same purpose the differences between the races of man, which are so strongly marked; I may add that some little light can apparently be thrown on the origin of these differences, chiefly through sexual selection of a particular kind, but without here entering on copious details my reasoning would appear frivolous.

If anyone is interested, you can find Darwin's writings on the web here. He was pretty prolific.