We trade with them, and they are poor. That doesn't make us the cause of their poverty. There are several formerly poor countries in East Asia that have become prosperous, or are in the process of becoming prosperous, by trading with us. How so? Is there some international conspiracy at work that coddles Taiwan, Singapur, and Vietnam but insists on exploiting Africa? 

Colonialism certainly wasn't primarily motivated by altruism, but most African countries have been independent for more than 50 years. Surely after such a long time they can be held responsible for their own fortunes. 

If you want to help Africa, fine, but there are better ways of persuading us to do so than this old, tired, phony guilt-tripping.