A minor correction. The brother who died wasn't a Marine. He was a scientist who spent time preparing for the science-based mission.
Fact: The CO of the Mercks asked the Jyrene to keep him informed.
The CO told the Marine that the 'Corporation' would buy him a set of legs in exchange for intel.
Fact: The hero of the story was being paid to be a corporate spy, not a soldier.
And, when the Corporation learned that the Na'avi wanted nothing that the humans had to offer, the corporate decision was made to use the mercenaries to drive to the Na'avi out of their home so the corporation could mine the alien planet to get the mineral ($20 million per kilo) what they wanted.
The Na'avi were given a choice. Leave your home or die defending it.
It is kind of humorous to see folks here siding with mercenaries who are killing solely for the sake of corporate profits.
We’re not siding with mercenary murderers, we’re siding against Hollywood scumbags who want to equate American and capitalist values with mercenary slaughter.