Group hatred is transmitted primarily through intergenerational oral storytelling of grievances

Evidence

Group hatred of this kind is transmitted in various ways. The oldest and most universal is through memory, stories told by parents or more often grand­ parents to the new generation, keeping alive and passing on the ancient griev­ ances and hostilities. The Balkan Peninsula and the Middle East are particularly rich in these, going back for centuries, some of them for millennia. — Bernard Lewis, From Babel to Dragomans, 1043