Either scientifically, or politically. They're just entertainment. Avatar had every "dances with wolves" and big-bad-company-wrecking- the-environment cliche in it too. And of course, the question of why any civilization capable of interstellar travel would need to operate a mine across the galaxy, even for Unobtanium, is never answered satisfactorily. or even brought up. And how many films now have the usual alien-human shoot-em-ups? Surely aliens would have nukes, and some defense against ours.

And if they need a villain, whatever is current and on people's minds will do. During the cold war it was communists, now its the big, bad corporations. I think we'd see a lot more Ay-rab villains too, if we didn't have plans to make money showing the films in the middle east, too. For a while there, South Africans (the white ones, at any rate) were the stock heavies. Then Mandela came along, and we had to go to "renegade Russian agents" as the bad guys, with the obligatory "good Russian" helping our guys catch Boris Badunov.

I was really PO'd when one of my favorite films, the Manchurian Candidate, was remade, and the old Red Scare villains replaced by a more politically correct evil corporation bogeyman. They had to stretch that one so far to make it fit the menace and horror of the original was lost, not even Denzel could save it.