It is easy to discover, beneath the politically correct themes (an honest white guy siding with ecologically sound aborigines against the "military-industrial complex" of the imperialist invaders), an array of brutal racist motifs...
The film teaches us that the only choice the aborigines have is to be saved by the human beings or to be destroyed by them. In other words, they can choose either to be the victim of imperialist reality, or to play their allotted role in the white man's fantasy.
If anyone should be offended it is us, inhabitants of modern technological society. Avatar's portrayal of alien tribal life is nothing like human tribal life, which has tended to be extraordinarily violent, more violent by far than modern life. While modern states like Switzerland and Ireland have shifted so far from war that it seems almost unthinkable, Lawrence Keeley's War Before Civilization points to extremely high death rates from intertribal war - most tribes fought wars at least once year, sometimes several times. Premodern tribes used total war: destruction of crops, mass-murder of women and children, enslavement of entire tribes and so on. Genocide was not unknown. Keeley calculates that the total number of deaths from war in the 20th century would have been twenty times higher were we all living in tribal societies.
Avatar cleans all that up and leaves the modern culture looking barbaric.
So Avatar is part of a political narrative, but the opposite one to what Zizek sees. Avatar is part of the Nobel Savage narrative, saying that sophisticated modern life is corrupting, and people in nature are happier and more peaceful. It's not true - modernity has brought peace from the chaos of constant war - but it is a fashionable narrative right now.