Barbara Hagerty at NPR just published an article asking: “Is the Bible More Violent Than the Quran?” I am not sure how one would assess whether the Bible is more violent than the Quran, but both books contain ample amounts of violence and encourage violence under certain circumstances.
If these books are read literally (and not sanitized by modern interpretations), they suggest that violence against enemies and infidels is acceptable. Indeed, the popes have cited the Bible to encourage crusades and imams have cited the Quran to promote jihad.
Sam Harris discusses these aspects of the Bible and Quran in The End of Faith: Religion, Terror, and the Future of Reason. It is not a pretty picture, and hundreds of thousands of people have been murdered in the name of Christianity and Islam.
My guess is that such violence is intrinsic to monotheism. Once you have decided there is one God and no other God/gods, you have created an in-group and out-group. This exclusivity, when combined with the belief that your religion is the “True” religion, establishes fertile soil for the flowering of violence.