It's best to be aware of the current professional evaluations when discussing this topic.
http://www.psych.org/public_info/media_violence.cfm
http://www.mediafamily.org/facts/facts_vlent.shtml
http://judiciary.senate.gov/oldsite/mediavio.htm
http://www.apa.org/journals/psp/psp784772.html
If one wants to be taken seriously in defending media and video game violence, one should - at least - have an awareness of these references.
My position on this is that it is clear from the currently available research that media violence has a negative effect on human beings.