thetathx1138, I'm afraid you're wrong. Why? You know those reaction bits where people are asked about how they feel 'prawns' will affect their neighbourhoods? Those are real, except the question was how having other cultures like Nigerians moving in.

So what? That doesn't mean Blomkamp set out to make "Solaris" in South Africa. It means his script needed a specific reaction from non-actors, so he did what he needed to get it. That's thirty seconds out of a ninety-minute movie.

As to agency, I think fanwank consensus is they are some sort of worker caste

That's a theory presented in the film, actually, although the movie seems to be intentionally leaving the cause vague.