One of the greatest evils arises when religion is combined with politics. There are multiple examples in history as well as today. One of the best examples occurred with the acceptance of the Dominican worldview of constant conflict between "good and evil" in the 14th and 15th century. They first targeted the Cathars until they were exterminated and then went after the other targets which led to the death of thousands, particularly women. The political establishment of the the day embraced the Dominican Order as a vehicle for propaganda and control of the masses. Enclosed is a nice paper from a sociological point of view about this horror:

The European Witch Craze of the 14th to 17th Centuries: A Sociologist's Perspective
Nachman Ben-Yehuda
American Journal of Sociology
Vol. 86, No. 1 (Jul., 1980), pp. 1-31

[daily.jstor.org]witch-hunts-began/

Today we are seeing the rise of horrific phenomenon again