The function of the critic is twofold: Identify what the author/artist/filmmaker is trying to say, then evaluate how well they say it. Many critiques have identified the anti-technology, anti-Western feel of Avatar, but to understand it, and why it influences so many people, you need to understand its philosophical roots.
The theme of Avatar is that technology corrupts and that only by being in harmony with nature can true happiness be found. Sub-themes include "Corporations are Evil" and "The Military is Evil." These themes seem strange coming from the most technologically advanced movie of all time, being produced, distributed, shown, and merchandised by mega-corporations whose freedom is protected by the military. How do we explain these apparent contradictions?
Is the message insincere? Not at all. It has been ingrained into certain intellectual elements of the culture for 300 years. The liberal/artist community really believes all this stuff. So where did it come from?
French philosopher Jean-Jacques Rousseau (1712-1778) popularized the concept of the "noble savage," perhaps better translated as the "natural man." Rousseau held that in a natural state man was compassionate and moral. He postulated that man reached his highest state when he came together in small related groups and learned love for the family, but before he became technologically sophisticated. This is the state of the inhabitants of Pandora, the Na'vi.
What happens when technology begins to intervene between man and the world? Corruption! Rousseau writes in his Discourse on Inequality:
The first man who, having fenced in a piece of land, said "This is mine,"...was the true founder of civil society. From how many crimes, wars, and murders, from how many horrors and misfortunes might not any one have saved mankind, by pulling up the stakes, or filling up the ditch, and crying to his fellows: Beware of listening to this impostor; you are undone if you once forget that the fruits of the earth belong to us all, and the earth itself to nobody.
Again, Avatar illustrates this philosophy be showing a society where nobody owns the land and where the true evil is produced by a corporation which wants to seize land and dig a ditch to exploit it for technology.