One of the doctors I work with is strong Muslim faith and he says he was taught by the Qua ran that taking a life goes against Allah, he won't even kill a spider (he laughed and said all bets are off for mice though). He also says that there are those that interpret it in such a way they can justify killing non-believers in the same way Christians like the Westboro Church interpret the bible in such a way to do the evil shit they do.
He also said those extremists play on the uneducated and hungry to further that cause.
So yeah, holy books (pick a book any book) give some nutjobs justification for a lot of bad stuff. We can't deny if you cherry pick those books that it says it what it says. Painting the entire religion with the same brush is where people go wrong. I know you are saying that already, so I'm not accusing you of it. It seemed at first you were denying those people exist, but this post tells me you get it.