Nonsense. Of course they are racially motivated, and of course the attacks happen with impunity because they are supported by the government.
The National Assembly just voted for expropriation of white owned farmland without compensation, in other words, race based theft by the government. Julius Malema, the radical who raised the issue in the legislature, notoriously commented last year that he was “not calling for the slaughter of white people — at least for now.”
Any person who hates racism sees the issue clearly for what it is. However, many racists find it convenient to use anti-racist rhetoric when their side is being oppressed while in principle caring nought for racial injustice. You can find plenty of racists on both the right and the left in America who use the language of racial oppression when their side is perceived as being oppressed who ignore alleged oppression when it happens to others. This certainly seems to be the case in South Africa.