"It is ludicrous to think that all of Africa's problems have been caused by some kind of racist, premeditated exploitation."
All? Certainly not--we didn't create AIDS. But most? If you watch a child drown, you are guilty of its death. Let me respond pre-emptively to some objections.
1) Yes, everything is more nuanced than this. I'm just providing information, not really making any case.
2) Yes, Africa's situation is deteriorating, which means it used to be better. I think this is because of at least 3 factors: 1) Western complicity with new, more efficient dictators; 2) AIDS; 3) the African infrastructure of the 60s and 70s was not as strong as it looked--the progress wasn't all real.