We lived in a Muslim country for five years. THEY have the same concept of sin that we have. Yes, what ISIS is doing is considered criminal and sinful to those Muslims who are good Muslims.
The Koran, after all, is really a knock-off of the Bible, MOSTLY the Old Testament. And yes, I happen to have a Koran too. My husband got it as a gift from his boss when we left the country (KSA).
That’s nice