It seems that race is an uncomfortable topic for many South Africans, especially many white South Africans. Specifically, the issue of white privilege. White South Africans swear high and low that white privilege does not exist, that they're the victims of reverse racism and that affirmative action has made it impossible for them to make a living in the country. They're tired of hearing about apartheid and how black people are still suffering. In fact, they're happy to tell black people to just “get over it”, like the subjugation of the majority of the population is something people can overcome with little or no effort.
Part of the problem, I think, is ignorance. White people don't experience discrimination at the same level as black people. It makes it much harder to express things like institutionalised racism to white people when they see affirmative action as a personal attack on their race.