Earth travelers' mission on Pandora is to extract the wealth of the N'ami by slashing/burning forests, dissing the natives, even killing them if necessary. (Remind you of anyone we know?)
Enter a former marine with two bum legs and indefatigible spirit to take up the mission bequeathed by his deceased twin brother: inhabit the newly gestated half human, half N'ami--go out, befriend then persuade them to relocate so the "bad guys" can get the goods. How he grapples with and ultimately resolves his dilemma is the stuff of the great morality tale.
My only reservation about this movie is that in convincingly resolving the dilemma, our energy to fight the real battle on the ground is dissipated.