First, let me say that this will not be as long as Mark's epic stream of consciousness review of 'Stupidity'. Second, let me say that this was a very odd movie that took me by surprise, but I think posed some interesting philosophical questions and so is appropriate for this forum.
A quick recap that will get you through the first 10 minutes of the movie without giving anything away: 20 years ago, a giant spaceship comes to earth and settles over the city of Johannesburg, South Africa. And that's it. Nothing happens. After a couple of months, people decide to go up and take a look. Commandos board the ship and cut into it and find thousands of aliens inside, starving and aimless. The aliens kind of look like 7 ft tall praying mantises (in any case bug-like). The humans 'rescue' the aliens and put them in a restricted zone on the outskirts of the city called District 9.
The suggestion is that the aliens have a 'worker bee' like mentality and they are missing their 'brain bugs' - so they can't fix their ship or take care of themselves. This also means that even though they have limited cognitive and language abilities, they can't really integrate with human society. There are tensions and violence between humans and aliens and the District becomes in effect a militarized refugee camp. That's the lead-in to the story and the beginning of the movie sees a documentary crew following a qausi-government organization that has been tasked with relocating the aliens from District 9 to a camp much further away from any human settlement.
One of the first questions that presents itself is whether and what ethical position the humans should take vis-a-vis the aliens. Given that they have space travel, they are clearly an advanced race of sentient beings. From a common sense perspective, I would think we would consider them as 'ethical equals' or at least acknowledge some kind of responsibility to treat them as we would other human beings (as opposed to insects or animals). And I suppose this means that we would expect the same of them.
But do we treat them as 'equals' with 'human rights'? Bracketing out the issue of political rights for a second (they are, after all, not citizens of the Earth, much less South Africa) we have to ask ourselves whether we have the same moral obligation to them as we do to a fellow human being. If so, why? They are, after all, not human. Do we assume that 'human' has really been a placeholder for 'sentient being' and that what we consider to be 'human' rights are really for anything that fits some criteria for sentience and perhaps other cognitive functions?
If you can even resolve this issue satisfactorily, the film further complicates the discussion by having humans only interacting with the 'worker' types from the alien race, who are more insect/animalistic and do not demonstrate the necessary cognitive function and awareness to be considered 'equals'. Beyond meeting criteria for ethical status, the aliens also really aren't able to enter into a 'social contract' with us. So we have a sense that we might have an ethical obligation to the aliens really only by inference to the parts of their race that must have been capable of building the space ship, but the actual aliens we are dealing don't have that capability and don't appear to be able to breed or develop into it.
Needless to say, the conscious or unconscious decision that the humans make regarding these questions dictate how they treat the aliens both at a 'policy' and a 'personal' level. And, if you are like me, you will find yourself reacting to the events as they unfold in visceral, emotional ways that are clues to how you answer the questions above.
District 9 forces reflection on the nature of 'natural' or 'human' or 'inalienable' rights. And while there is a clear social message (I read the film at least in part as making a commentary on the treatment of ethnic minorities or aboriginal cultures in Africa and elsewhere), I think the movie elegantly challenges our assumed anthropocentric concepts of ethical agency and philosophical justifications for moral positions based on rationality or sentience.
OK, I lied. This is as long as Mark's post. I guess we are equally prolix.