As I've been reading the HoD, I keep coming back to the concept of "Ethnocentrism." As I have listened to discussion, I keep coming back to the concept of "Ethnocentrism." None of my students have brought up "Ethnocentrism," so I thought I would--here on the blog.
1. This link is to a definitions of "Ethnocentrism." I think the first two, will give you a good idea.
http://www.google.com/search?hl=en&defl=en&q=define:ethnocentrism&ei=B7rLSc3xM-PfnQec8qDwCQ&sa=X&oi=glossary_definition&ct=title
2. This link is to an Anthropology site at Indiana University Indianapolis. It's more in-depth, but some of the explanations might put the concept into perspective for you.
http://www.iupui.edu/~anthkb/ethnocen.htm
3. This link is to a site my a College that prepares people to be missionaries for the Church of the Nazarene. It will give you their perspective on the issue and why it's "bad."
http://home.snu.edu/~hculbert/ethno.htm
I hope you'll take a look to get an idea of what ethnocentrism is. I think it will help you understand Heart of Darkness.