Any belief system that claims to bring peace by killing everyone who disagrees is extremist.
I had a discussion with a visiting JW gal few years ago. She actually was using recent terror attack as a sign of the end. I asked her if she was aware that Isis believes they will bring peace and moral purity by their killing. She said yes.
How then can you see them as terrorists, I asked, don't you feel the same way?
She insisted the difference was God was doing the killing.
I asked if God asked you to do it with him, wouldn't you? According to the Bible God told his worshippers in the past to kill entire civilizations.
She paused.
So to worship the God of the Bible you must be willing to kill people.
There is no moral superiority to endorsing the killing of billions over doing the actual killing. The only difference is when Christianity spawned, the Romans had control.