Demonization is the portrayal of another group as all evil.
It may occur in:
(1) religion
(2) politics
(3) society
(4) any conflict
The demonizer often amplifies his or her good while attenuating any faults, while simultaneously performing the opposite on the demonized group.
The demonizing group does this for a reason:
(1) In a world of Good and Evil, fighting evil implies that the demonizers are good.
(2) The demonized group becomes a legitimate target of anger.
(3) Any brutality against the opponent is not only justified but meritorious.
(4) It helps a leader to manipulate followers who are encouraged not to question.