Eli13
Fish Dreamer
Because nukes in space are banned by treaty. The corporation in the film is allowed to operate and have its security detail on Pandora if they abide by certain rules.
Nuking stuff might not have been that effective, either, and if someone did decide to nuke Pandora, they would have to wait roughly 7 years to ship the warhead there...
And they're actually trying to avoid killing the natives, because naturally it gets bad press back home, until General Ripper goes insane and takes control of everything...
It was a joke? Most of here are aware they're banned by law. But then again we dont know if they are still in effect. BTW, who says they had to go back? Did you check the cargo manifests? Cuz I didn't, but you don't know whats there.