Group-think influences how members will act out.

Group-think provides the illusion of invulnerability, the capacity to ignore warnings and to construct rationalizations (no matter how nutty), the comfort of unquestioned belief in the inherent morality of the group, targets for aggression (Others, whether in-group or out-group), and the Holy Grail – um, Holy Idol – of “correct thought”.

Best of all, group-think provides absolution for all atrocities committed under its name.  Individuals can commit wrongs as members of a group that they would never have committed as individuals.

Menninger listed examples (101-123).  Each of these examples raises, in its own way, the question: Why would individuals want to commit wrongs (as part of a group) that they never would have committed as individuals?