There is a powerful discussion of segregation in the novel, particularly because it is generally viewed through the character's eyes rather than simply discussed. But along with those visions of the causes and effects of the segregation comes the discussion available to the reader through the documents found in Arthur Jarvis' home that his father pores over after his death.
The idea that segregation is caused by the combination of both idealism and base human instincts is a powerful one. James suggests that the white population often has great ideals of doing right by the natives but then their natural selfishness and their great fear takes over to often create policies that stigmatize and brutalize the native population. This in turn only serves to highlight the negative parts of the white populations' feelings such as fear and protectionism which ends up drowning out the idealism they truly feel.
This is of course in contrast with the newspaper and other political writings that capitalize on the fear and disgust of the white population and push for more exploitation of the native population and stronger segregationist measures. The juxtaposition of the two viewpoints also helps to flesh out the discussion of segregation in the novel.