The people who hate Spider for saving Quaritch need to stop acting like Spider leaving him to die would have made anything any better.
If Quaritch died, then Lyle would have been promoted to coronal as the only one of his squad to survive, he would have taken Jake in immediately when he found him in AFAA, the kids would have died at the hands of the Mangkwan because Jake and Quaritch weren't there to save them, and Neytiri would have lost her entire family in one day.
Edit: Thank you comments, they reminded me about the Tulkun hunt. The RDA would have completely annihilated the Tulkuns, rendering them extinct in that area because Loak wouldn't be there to get Payakan to convince the Tulkun elders to give up their pacifism. The Reef clans wouldn't have even known about the attack of the calf communion if Jake wasn't there to tell them.
Without Spider there, not even just to save his dad, the entire story falls apart and everything would be worse off for it.
