I used to have a similar stereotype about (white) South Africans who I met in my country. However, after having spent some time there recently I can say that South Africans (of all ethnicities) are absolutely lovely people. I was really impressed with what an integrated and truly multicultural society they have less than thirty years after the end of apartheid. I realise there are still big problems but it left a big impact nonetheless.

My hypothesis is that all the shittiest people left when apartheid was ending because they didn't like black people having human rights, and fled to majority-white countries.