I thought the holy book of the Allah followers didn't say anything about killing non-Muslims.
In fact, all major religions I know of that have ascended beyond cult status preach that violence and killing is wrong. And the "Golden Rule" is present in one form of another. And since all religions formed for pretty much the same reason, would it not follow that all their ethics are essentially the same?
And if the rules of religions define sets of ethics, and there is conflict, how would you decide which set of ethics is ultimately correct?
Also, all RELIGIONS are real; it's the various concepts and "beings" they're based on that are up for debate.
See, this is why I don't believe in any sort of religion.