In Sven Lindqvist's Exterminate All the Brutes, the author travels through parts of Africa with a copy of Conrad's Heart of Darkness, reflecting both on that text and on the historical context of the book. What Lindqvist means in this passage is that the history of colonization (the "Scramble for Africa") is there for anyone to read about and study. It's hardly hidden. Part of his goal in this book is not only to relate the history but to engage with it and to interpret it. This is what he sees as essential, and this is what he sees many people reluctant to do. Partly it's because it is such an unpleasant and disturbing history and partly because a thoughtful person will not only have to confront violence and brutality but will have to reflect on what this says about humanity.
Lindqvist also makes a link between European's violence in nineteenth century Africa and the genocides of twentieth century Europe, especially the Holocaust. It brings up some unpleasant truths about human nature and humanity's tendency toward dehumanizing others and toward genocidal violence. It also calls into question the perceived superiority of white European culture, which many think is the source of all that is good in the world: politics, science, art, literature. Yet if Europeans are capable of such barbaric practices, all in the name of their civilization, it undermines any such claims to superiority. It's these unpleasant truths which Lindqvist thinks people have trouble with but that he believes they need to confront when thinking about this dark historical period.