I think that the argument that violent video games cause this, is utter rubbish, and there is absolutely zero conclusive empirical evidence (that isn't full of hundreds of confounds) supporting the argument that they do. I have played every violent video game you can think of, and it has not either increased my levels of aggression (which are pretty low) or desensitized me to real violence and death. One thing that I have a lot of difficulty doing, is watching incidents of real death. Heck my profession (clinical social worker) is all about sympathy and compassion. I play video games for fun, and I enjoy them... why? Because... they are not real, at all.
This video does a decent job of expressing the concept.
Warning, the following video contains a segment where a real person kills themselves. You can skip that part (as I did), and instructions are included in the video. It also contains swearing.
http://www.escapistmagazine.com/vide...ed-to-Violence