Those that are not Catholic and do not have a shared body of knowledge...what about them?
I don't have any problems answering sincere questions, but I tire easily of debating my religion with people who just want to argue. I see no point in it. I will not stop being Catholic and you will most likely not become Catholic, so what is your motivation? Is is knowledge? There are plenty of links to read. If it's just to bait and parse words, I think we all have better ways to spend our time.
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).