Good question. I was reading an article this morning that mentioned this. I haven't thought about that but it makes sense.
-Geaux
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The extinction of ISIS
Some argue that Muslim religious authorities ought to excommunicate ISIS, and that would solve the problem. Though rather rare, excommunication has taken place in Muslim history — but not on the grounds of sinful actions, grotesque though they might be. Criminals can be punished or fought against, even killed; but traditional religious authorities insist such criminals must still be recognized as Muslim, unless they repudiate core Islamic theological beliefs, like the unity of God, for example. Ironically, it is heterodox movements that regularly resort to excommunication for non-theological reasons – indeed, ISIS appears to do that regularly.
This stupidity needs to end Why the Atlantic NY Post are clueless about Islam - Salon.com
-Geaux
-----------------------
The extinction of ISIS
Some argue that Muslim religious authorities ought to excommunicate ISIS, and that would solve the problem. Though rather rare, excommunication has taken place in Muslim history — but not on the grounds of sinful actions, grotesque though they might be. Criminals can be punished or fought against, even killed; but traditional religious authorities insist such criminals must still be recognized as Muslim, unless they repudiate core Islamic theological beliefs, like the unity of God, for example. Ironically, it is heterodox movements that regularly resort to excommunication for non-theological reasons – indeed, ISIS appears to do that regularly.
This stupidity needs to end Why the Atlantic NY Post are clueless about Islam - Salon.com