Dehumanization is the psychological process of demonizing the enemy, making them seem less than human and hence not worthy of humane treatment. This can lead to increased violence, human rights violations, war crimes, and genocide.
Dehumanization is a psychological process whereby opponents view each other as less than human and thus not deserving of moral consideration.
Jews in the eyes of Nazis and Tutsis in the eyes of Hutus (in the Rwandan genocide) are but two examples. The more severe the conflict, the more the psychological distance between groups will widen. Eventually, this can result in moral exclusion. Those excluded are typically viewed as inferior, evil, or criminal.