The most compelling difference between the American debate, and the South African debate is argument of land ownership.  As an American, I don't know the history of South Africa and the claim to the land in question.  Of course, in America, we have the parallel issue of claims of Native American Tribes.
 Every community in America wasn't founded upon a native tribal settlement or village.  Near Plymouth, Massachusetts there was an Indian village that was wiped out previous to the Mayflower's landfall.  I know of American towns that were founded by Europeans away from native villages.  
 The crux of the matter is this question.  Is it immoral for a person to live, explore or settle in a foreign land inhabited by people with physical traits other than their own?  If black South Africans can't tolerate white people, then what is their proposed solution to this issue?

@Jenna ah It's interesting to hear that the (at least some of the white) South Africans have a similar view of their past racial barriers as some Americans do with pre-civil-rights movement. It seems to all come down to which degree it impacts people today and what to do about it. There's an agreement that the appropriate response be proportional.