As I understand it, the opposition to the TMT isn't a NIMBY issue: it's more about a historically ignored group trying to gain influence over issues it cares about.
In this case, "I don't want another giant telescope on my culture's sacred mountain" isn't about astronomy at all, it's about the culture (and the larger perspective of indigenous interest in local resources, and respect for a pre-existing treaty that wasn't quite honored -- these folks aren't primitives or hippies, they know very well this is a political process in the real world).