It is well known that the Holocaust act of racial cleansing of the Jewish nation by Nazism led by Hitler during World War II was based on racism. However, the social, personal, and historical reasons behind this behaviour are diverse. In addition to explaining some existing historical and personal reasons, this article will use scapegoat theory and social identity theory to specifically analyse racial discrimination. The social reasons behind it, and thus reflect on explaining the reasons behind some social prejudice phenomena and how to avoid social prejudice caused by such social reasons in today's society.