Theodore Roosevelt said, "The settler and pioneer have at bottom had justice on their side; this great continent could not have been kept as nothing but a game preserve for squalid savages."
It was the economic developed spawned by the needs of the global economy that threatened the Guarani' people, not military intervention or interethnic relations.
The nation-states are doing what capital controllers are supposed to do: choosing modes of production and ways of life that will bring the greatest immediate monetary return.