Well there is no doubt the members of ISIS rejoice in their depravity. Daily Mail has photos every day of ISIA member holding buckets of heads and heads on pikes.
It’s difficult for many people to understand how they can be this way because they have no understanding of how these people are raised and indoctrinated into these sects.
For many who join these terrorist groups it’s like Americans who grow up wanting to join CIA or Special Forces. Only they view it ‘all’ through the eyes of Islamic teachings.