Keep in mind most of the audience will not question the suspension of disbelief to that extent. It worked for Star Trek and Star Wars, and a number of other fantasy universes. On the other hand, you can't have a love story gone unquestioned if your romantic interest looks like a far more believable alien, such as Giger's Alien or perhaps the arachnids from Starship Troopers.
You could also argue the film didn't need romance to work, and I would love if the general audience hadn't been conditioned, in decades of filmmaking, to expect this formula. But that's how Hollywood works and has always worked. Most successful scripts are different versions of the Hero's Journey, with a fair share of romance, one or two plot twists and the triumph of good over evil. You can't blame Cameron for that.
By the way, for the sci-fi geeks, Ain't it Cool has a very interesting (and well written) article about the science of Pandora: http://www.aintitcool.com/node/43440
I'm sick of anti-white/anti-west propaganda trash films thinly veiled as "fantasy films" such as this that Hollywood keeps spewing out.
Oh, the big bad EVIL AMERICANS killing the Natives...gee...typical.
The analogy is so blatant.
Err, you do realise this is an american movie made by an american director? I believe you're missing his point. It's surely an anti-war movie, very in touch with everything that is happening around the world. And all the "good" human characters are still americans who have come to realise mass slaughter is not the answer to settle any ideological conflict. Some don't even undergo this change of character, being "good" from the time they appear on screen. I think Cameron did a good job at showing different points of view despite of racial boundaries.
If anything, this is a very pro-west movie, in the sense marines are portrayed like terrorists, killing civilians and destroying their homeland in order to make a statement. And what actually moves the plot forward is how these terrorists are disrupting the balance of Pandora.
There are though, some Bush era references (terror against terror). They're anti-west, if you sympathize with authorities waging wars for profit (oil - unobtanium), which is also another form of terrorism, as implied by the script.