It appears the Rockstar team watched a few documentaries that take advantage of Brazil's dark beauty, as it's able to name-drop such titles as Favela Rising and Bus 174. So, we're sure the devs were completely prepared for the reality of São Paulo's slums.
Update: As many of you pointed out, Favela Rising and Bus 174 are both set in Rio de Janiero, and Brazil is home to many non-violent, wonderful people and places. Rockstar is setting a scene that scare-based media and PBS has been harping on for years, probably because shooting people in an innocent, beautiful environment just doesn't feel right to the developers. Or they wanted a free trip to Brazil.