I hope that this didn't actually happen

I get that South Africa has had a very turbulent very recent history of horrific racism and that there are white people in the country who do continue to benefit as a result of policies enacted during the apartheid era, but this person is just some girl trying to make a living working a very menial job. There's a lot made of privilege and power imbalances in identity politics but doesn't the writer here realise that the relationship between her and the server being just that, a servile relationship puts the power imbalance in HER favour? Too often liberal politics ignores one of the biggest disadvantages a person can face is class and wealth, mainly because a lot of people who have the ability to invest themselves in these issues are very middle class and don't want to consider their own privilege over those less fortunate than them.

Also saying that refusing to tip a server is "so black" has unfortunate connotations.

tl;dr: if you want to fight injustice, you should be punching up, refusing to tip someone doing a menial job for shite pay is the furthest away you can get from that without setting a homeless person on fire or something.