Well its understandable to a large degree. Nirvana gave the masses distortion and self-hating and angsty lyrics, the post-grunge sound is too omnipresent. If they don't sound like Nirvana, then who do they sound like? And if they "don't sound like anyone" then we've got a real problem.
They take from Nirvana heavily and its rather obvious that if nirvana never made it to south africa, seether would be playing dave matthews-esque music or whatever else was popular.