The scientist didn't have to be a good unselfish person. Just like Ann and the reds in the novel Red Mars, they are stubborn, and have biases to their priorities (preserve Mars as it was) that don't necessarily align with the greater good of humanity.
Sigourney is not supposed to be the voice of reason, (which would find a compromise ) but one of the ends of the spectrum.
I don't have any problem with her character being selfish, but as she studies the Navi she takes up the point of view that disturbing them isn't worth mining for rocks. Well, okay. But, as she sets her self up as their advocate among the mining company employees, she stops doing her job of trying to communicate with them. What's worse, all the while she's building up this idea of herself as an advocate of letting this strange new society be unmolested and stay pure to its self,
she doesn't actually advocate for the Navi. She never comes up with compromises that will allow them to remain unbothered, or just be less bothered, by the mining operations.
She talks so much about "stupid soldiers" killing them, but instead of coming up with ways to relieve tensions between the groups, she just insults the humans and ignores the Navi. The storytellers have put her in the middle of the two factions, and throughout the miners are constantly telling her and her team "we have our interests, you know what they are, help us tell the Navi about them." Not only does she not tell the Navi about the mining operations, she never goes to the Navi and asks them what they want or how they think the miners could improve things. That's not a problem for some random character, but it is a problem for a character whose job is being a diplomat, and its an even bigger problem for a diplomat who is constantly being asked to do diplomatic tasks. What's more, when she
knows that the miners and the mercenaries have active plans to destroy the Navi city she doesn't breath a word of it to the Navi. She knows that they're going to be killed, but doesn't warn them to leave or prepare to defend themselves. She just leaves them to die.
She completely abandons the job she's there to do, and ignores all requests to do it, even when it aligns with her own stated ideals. Why would she do that?
I'm not defending the plot or anything like that, but if someone is doing the job they are paid to do, that doesn't free them from bad guy status. Think of how much evil bullshit happens in this world where people are 'just doing their job'.
Human trafficking, poaching, assassins.. If your biggest worry is the money you make, you could be an asshole.
Ribisi's character, and the head of the mercenaries, are actively trying to gain access to mineral deposits without fighting. They're willing to fight and kill for them because they're ruthless, but they do make an effort not to do it.
So that was my argument; They may not be good people, but they aren't blackhearted villains hellbent on killing for fun and making money no matter who it hurts.
