A good starting point is to look at the history of Africa.
Show me their civilizations over the last 5000 years. They didn’t happen. Central America/ south America had incas, Mayans, Aztecs... you can go into the jungle and see their ruins today, but, Africa does not have ANY evidence of one excepting perhaps a brief “great” Zimbabwe.
I have to believe that the white man oppressed them then too. (Actually, the muslims were very active there)
A excellent video is http://www.youtube.com/watch?v=cT_RSDeAYjI