the violence is not what sold the film...cameron himself said that what they found is people cared more about the actual planet not the big action scenes
From a storyteller's viewpoint, yes, everybody cared about the planet and the blue people . . . but because they were under threat by the military wackos. There are different ways you can have heroes, you have somebody fighting an evil presence (like the military), or people who overcome difficult situations that are nobody's fault. You actually have both in Avatar, the paralyzed soldier overcoming his circumstances, and the blue people overcoming the "evil" folks, as well as some subplots. If you had a movie about a planet of blue people where they don't have to overcome the evil military folks, but perhaps deal with a planet wide, uh, fungus that is trying to kill the home tree or whatever, it would be less interesting to some.
Cameron took the short cut that big blockbusters like Star Wars, Harry Potter, and many other make by personifying evil in people, corporations, . . . emperors who throw lighting bolts. The movies that are harder to make involve less obvious sources of conflict/tension, and they usually outperform in terms of academy awards and such. In Titanic, the "evil" was a combination of mother nature and I guess some human incompetence, as well as some tension between the classes, it was less obvious as Mr. Future G.I. Joe pointing a weapon in the face of a race of blue people living in perfect harmony with their planet.
Obviously, if you get my point, people cared more about the planet and blue people, that was how the story was constructed, in which the military plays a crucial role. Sort of how Casablanca uses World War 2 germans for tension, and are integral to the story, but the viewer doesn't identify with them.
Avatar is much more violent than Casablanca, and they are selling Avatar action figures, most of which are armed, armed blue people, armed military psychos and their killer robots and stuff. For a lot of men the action/violence made the film appealing.
Avatarland without the military whackos would be less recognizable than the films, as presumably the military characters won't setup shop. It'll be the same as an Ewok village, an interesting environment most folks would like to walk around a bit after seeing Return of Jedi years ago, but not a lot of interest outside of interesting plants.