A state of mind where the new and unfamiliar are denied. The idea is that this is an effective
defensive posture. Suspect everyone. Crush
dissent.
Expel malcontents. This is a
pejorative term. It is no fun to be around the bunker mental.
Usually, a bunker mentality is evolved as a temporary response to a perceived threat. All too often, it is maintained beyond the point where it is of benefit. People forget the way things were before the walls were put up, and just assume that only evil comes from the outside, and only good from within.
It usually takes a group of people, feeding on each others' paranoia, to develop a nice, robust bunker mentality.