Since the beginning of time, people have used religion to justify commiting sick crimes. How long ago was it that "Christian" men and women held another race against their will by saying that We, Black people, were the sons of Ham, and therefore we good for slavery, and oh, by the way, slavery is in the Bible, so it's good?
People ALWAYS re-interpert old laws to use them for their own agendas. The Qu'ran strictly prohibits the acts of violence that are commited by a few, uh, "misguided" people. The Bible does too, but that hasn't stopped people for over 2000 years.
Were they religious? They may have believed in their faith and gave praise to Allah, but were they living by the laws as they should have? No. And most of us, in ANY religion, do not follow the laws of our religions exactly as we should.