In under a month Avatar has racked up nearly a billion dollars from outside the USA, bringing its total box office to $1.3 Bn+ at the time of writing. It will be the biggest box office earner of all time. Money talks, especially in Hollywood.
So what is being said, exactly?
Please don't read until you've actually seen Avatar for yourself.
The earthlings are there to take the valuable rocks. That's all that's motivating their mission, and it is non-negotiable. Those in charge prefer to use a minimum of violent force, as that is politically easier to sell to the people back home. Atrocities are more work for the PR machines, but that doesn't rule them out.
This conflict is analogous to the last few millenia of human "civilization." Much about the Na'vi seems familiar to indigenous tribes here on earth. Much about the human mining enterprise seems familiar to what we know today as imperialism.
Writer/Director James Cameron takes it a step further and brings the conflict up to date. Lines like "shock and awe" and "fight terror with terror" pop up. The justifications used to demonize the Na'vi are heard on America's airwaves today, demonizing humans half a world away. Race, religion, culture, skin color, that which divides us is exploited and played up.
While demonizing another species like the Na'vi may seem easier to pull off than racist or nationalist smears here on earth, 2010, Cameron has done something wonderful with his central plot. He bridges the gap between human and Na'vi by combining their DNA in the lab. The "Avatar" of the title achieves its own place in the (film) history books by offering the audience the means of jumping species over to the other side. We actually go over to the Na'vi side with the leading character Jake Sully.
As Jake Sully becomes more and more Na'vi, we can't help but see his original employer as the villain. As Sully, who only controls the human/Na'vi hybrid, and is not actually the creature, becomes more and more native, we must conclude that the Na'vi are correct to resist the mining operation and the mercenaries. The indigenous resistance is legitimized, and we would do the same in their position.
With cinematic mastery Cameron escalates the conflict. The invaders are technologically superior, and their military arm is ruthless in the extreme. Willfully ignorant, racist and calculating, they plan on destroying the planet's most holy site in order to demoralize the Na'vi. This plan will attempt to kill the planet's living God, something the earth military force doesn't believe is real, but the film's audience sees that it actually exists. That attack is the "shock and awe" strategy, the "fight terror with terror" moment.
The earth force is full of such hubris and such a sense of invincibility that it's a pleasure watching them get their asses kicked. They lose because they deserve to lose. They have no legitimate claim to what they seek (the planet's mineral wealth), and no moral right to be there at all, not by force.