I think it's best to reply to each point in turn.

Access to proper education, not bantu education.

This is relative privilege. That is, he didn't go out and force blacks to have a lower standard of education. It was an endemic problem, but his relatively better education doesn't mean he benefited from oppressing black people. His standard of education was on par with most other first world countries around the world at the time. It's better to realise that black people suffered a below-average level of education, and this disadvantaged them. It's not excusing this disadvantage, but it is disputing that my uncle benefited from it. An important distinction.

The permission to work in which ever field they felt like.

This is the same distinction as the previous point. This isn't a benefit, it's a natural right. Would you have preferred he be discriminated against? Surely not. The problem is the disadvantages blacks faced.

Land taken from non-whites given or sold at low cost to whites.

He was given no land, nor was he given special land previously owned by black people. Few white people were. The majority of these land grabs were by large corporations and powerful people who managed to lobby the government.

Being able to live in the city you work in, rather than having to commute in from poorly developed townships.

The same distinction as points one and two.

Whites account for 10% of the population, but still control the majority of the economy.

How does he directly benefit from this? This demonstrates the endemic issues with racist policies, but he still had to work hard to earn his station.

The problem with listing various relative advantages is that these aren't direct benefits. Instead of seeing what happened to the blacks as discrimination, you see what happened to the whites as special benefits. Perhaps the problem is in the definition. Few people will argue white people had a relative advantage. But on a world scale, they were simply afforded the same rights as people in other Western countries. I suppose my real concern is with the justification that, because some powerful white people and companies managed to exploit the black population, my uncle was somehow responsible for that, and now deserves to be fired and ostracised.