And you are correct - white people aren't allowed to "protect themselves" by engaging in mass murder, organized oppression, and social violence against black people. Apartheid was and is evil.
Alexa, what is necklacing?
While life for white South Africans is more difficult than it was during Apartheid, for obvious reasons, and they now have to contend with affirmative action in many jobs and preferential procurement in government tenders, as a group they still have an inherent historical advantage compared to other racial and ethnic groups in the country.
There's a reasonable argument to be made as to whether those redress measures remain valid, fair, economically beneficial, or necessary, but what's entirely unreasonable is to claim that white South Africans today receive anything even resembling the abuse, restrictions, limitations, and indignities experienced by non-white South Africans under Apartheid. They're not at all comparable.
[0] https://www.statssa.gov.za/?p=14606 [1] https://www.timeslive.co.za/news/south-africa/2019-11-18-whi...