Siege mentality

A siege mentality is a shared feeling of helplessness, victimization and defensiveness. Although the term evolved from real sieges, today it refers to persecution feelings by anyone in the minority, or of a group that views itself as a threatened minority.

Siege mentalities are particularly common in business, the result of competition or downsizing. Some churches may have this paradigm, particularly if they are not traditional mainstream groups. Dictatorships have been known to encourage this point of view among their own people, since it justifies the continuance of those in power. A current example that seems to be fairly successful is North Korea. 

This is also very commonly used in the field of sports, where coaches or managers often create a siege mentality in their players by highlighting an environment of hostility from outside the club (whether or not the hostility is real or exaggerated doesn't matter).