An article in Nature earlier this year showed what many of us have also encountered in the classroom: reading violent Scripture makes violence seem acceptable to the reader. At least, in my experience, it makes readers who would in any other context deplore actions, instead approve and justify them because they are found in Scripture.
I have not seen evidence that such people actually become more prone to violence. But they do at the very least learn the art of justifying things that do not fit with their usual moral and ethical sensibilities. And that, I feel, is a disturbing thing for one to learn from a religion.