Why do South Africans hate Nigerians?

Chimamanda Ngozi Adichie writes:

South Africans and Nigerians (and indeed other African immigrant groups) have simply not had the time or the neutral space to grow an organic understanding of each other. The Nigerians arrive with their different, more distant colonial experience, with their mercantile spirit, with none of the conditioning of the South African menial wage-earning experience and – yes – with that swagger. They arrive in a vulnerable country where the legacy of institutional exclusion still thrives. They create spaces for themselves in whatever way they can and, of course, they arouse resentment.