One can critique the film's plot as not being especially deep, but that doesn't make it wrong. If it's at all helpful to the wingers, this kind of thing happened and is happening all the time. Instead of white Europeans and Native Americans, I saw a similar process in Burma between the ethnic Burmese military junta and the minority/hill tribe Karen people where the junta wanted to run a natural gas pipeline to Thailand, (with French and American oil company help). Jared Diamond's book Collapse discussed how gun-wielding Maori decimated the hunters of Chatham Island.*
I'll make these critiques of the Avatar story line in terms of accurately depicting our world:
- The natives remained completely united. That never happens. The colonizer always finds allies among the natives, exploiting existing rivalries and tensions.
- The natives don't want anything the moderns have. That's not true, although they might be better off without much of it - alcohol, opium, shiny beads, guns, and saggy pants.
- The natives are completely good. Also untrue - instead of bad guys versus good guys, the real world is more like bad guys versus less-bad guys. The distant or maybe not-so-distant ancestors of the natives almost always did what's being done to them, taking the land from someone who was there first. I doubt there's any human society that didn't do bad things on a regular basis to themselves or their neighbors.
None of the above excuses the worse sins of the invaders, of course.
We could say these aren't flaws in Avatar because the natives aren't human, but then it's also not much of an allegory for this world.
*Wiki does claim the Chatham Islanders were nonviolent, which strikes me as complete bull.