I would rather think it is the other way around.
Humans are offering racial immortality. (of sorts)
The Na'Vi are screwed if/when a meteor hits the world, solar flares erode the magnetic field holding the mountains in the air, etc... or failing all that, the sun(s) burns out.
If you have space faring tech, and not just any old spaceship but a feasible interstellar drive, your race (and whatever biological lifeforms you bring with you) is effectively immortal short of an interstellar war wiping you out. And even that is freaking difficult, the survivors or desperate disaspora will create immeasurable colonies that become practically impossible to physically track down and exterminate. (should anyone be even attempt to try such a monumental task for minimal gain)
Furthermore, to bring a potentially xenophobic society (can't predict cultural reactions. They might be...) into the interstellar medium risks a future extinction for humans. After all, if they accept the tech and later some racial divide causes a war and humans lose, we die. Compared to the current situation of "only humans have starflight", we are going from basically 0 risk to one (still small but) much much higher. It's an off-chance, but the risk increase is orders of magnitude from negligible.
We're basically offering them this trade: "share these rocks with us, and we'll share the universe with you". The damned rocks and your religion are an incomparably small price.
All for your bloody rocks. When we could just take it when the political situation gets worse back home. What do you think happens when the oil-equivalent mining company goes comes back with a truckload of war casualties and nothing to show for it? The price of unobtanium will skyrocket, that's what. And sheer economics will make humans come back, and the greedy capitalist might not be so nice this time...