The author is with ICSR @ Kings College and attempts to answer so many questions. The title is: How religion can drive someone to slaughter his fellow citizens – and believe they deserve it.

A key passage:
The movement is, however, millenarian; its followers believe that they are helping bring about the change of a corrupt society, transforming it from evil to good. Once they accept this as their mission, almost any act which is perceived as helping further the project, no matter how horrific, becomes acceptable and legitimate.
Link:http://www.telegraph.co.uk/news/2016...-citizens--an/