Students and critics alike often argue about whether Heart of Darkness is a racist book. Some argue that the book depicts Europeans as superior to Africans, while others believe the novel attacks colonialism and therefore is not racist. There is the evidence in the book that supports both sides of the argument, which is another way of saying that the book's actual stance on the relationship between blacks and whites is not itself black and white.
Heart of Darkness attacks colonialism as a deeply flawed enterprise run by corrupt and hollow white men who perpetrate mass destruction on the native population of Africa, and the novel seems to equate darkness with truth and whiteness with hollow trickery and lies. So Heart of Darkness argues that the Africans are less corrupt and in that sense superior to white people, but it's argument for the superiority of Africans is based on a foundation of racism. Marlow, and Heart of Darkness, take the rather patronizing view that the black natives are primitive and therefore innocent while the white colonizers are sophisticated and therefore corrupt. This take on colonization is certainly not "politically correct," and can be legitimately called racist because it treats the natives like objects rather than as thinking people.