At the end of the program, the primary reason RSA developed nuclear weapons was to force the hand of Western powers into interceding if RSA was losing a convent

At the end of the program, the primary reason RSA developed nuclear weapons was to force the hand of Western powers into interceding if RSA was losing a conventional war (help us or we'll start nuking cities). They had zero interest in detonating a nuclear weapon just to kill black people, especially not on their own territory. RSA intelligence services certainly investigated things like race-specific diseases, but that's not what the nuke program was for.