Since the game was spread out in time, this permitted retaliatory defection - which isn't part of the original non-iterated PD, nor is refusing to play.

And since the Na'vi choosing to fight turns out to make human non-cooperation give a far worse outcome to them than cooperation it just isn't a Prisoner's Dilemma at all. It's a "The Na'vi are will F@#$ you up if you mess with them" game.