I argue that it wasn't really Nigeria as a country that they were pointing at but humans in general and our somewhat savage and prejudice nature. The thing is, places like that are a cruel inhospitable and terrible places to live. There is war, poverty and disease. The aliens in District 9 were a metaphor for that.
I say don't hold back, we shouldn't sugar coat the world and pretend it doesn't have problems just because acknowledging that it does gives us a bad rep. We have to accept the world as it is, we have to wake up and realise the truth. That's what I think.
This was a movie, I do not hate Nigeria after watching this movie. I found myself more or less thinking that there are simply problems with this world and problems with our nature in general. They were referancing issues like Apartheid and prejudice which is still a real issue in this world of ours whether we like it or not.
Also I'll wrap this up by saying that the film makers were actually displaying a human side. Because yes there were sociopaths and gang leaders and savages and racists in that story, but also presented were people protesting the forced eviciton of the aliens and a few people speaking in their defence. It showed that there are bad people but there are also good people, this goes for Nigeria... and the entire world.