People might hurt or even kill for their belief if they think and are convinced that what they are doing is right. Of course, any faith that tells and promotes hurting others should be checked as we have to learn to respect everyone.
I have been involved in both wars and revolutions. Seen both good and bad things done; BUT what drives me to a rage, is when these poor girls that were taken captive by ISIS, enslaved, raped, traded, sold, degraded, and more, are finally freed and return to their families, are then killed or driven away by there own family members because they have dis-honored the name of the family.
This not isolated, but common in may parts of the world.