This is obviously an ongoing debate, however I am covering this topic as a project in college and am looking for views on this topic from anyone. People may want to talk about cases like when a teenage boy killed his friend with a hammer and blamed it on the game Manhunt.
They promote it as much as music, film, books and comics do. At the end of the day, if a small percentage of users out of millions decide to go batshit insane and bludgeon a bloke to death with a 5-iron, I can hardly call that conclusive evidence that these mediums actively promote violent behaviour.
All forms of media present us with ideas anytime we view them. Movies, music, video games, books, newspapers, magazines, etc. People can blame the medium of their choice but the bottom line is that a healthy mind is not influenced solely by one source. There are typically underlying problems that far outweigh on source that may have pushed them over the edge or given them an idea. Plenty of gamers are like me. We play violent games a lot and we have nothing to show for it. I'm a calm dude and I'm not an aggressive person but my favorite games are Resident Evil 5, Fallout 3, Modern Warfare 2 and Saint's Row 2. All are extremely violent or vulgar (or both) in nature but because I'd like to think that I have a fairly decent handle on reality I don't copy them because I know that I'll only get myself in serious trouble, hurt the people I love, or possibly get myself killed. People who are unable to distinguish fantasy from reality are those that are typically persuaded by gaming.
I'll give you an example I used in my college years during at least 2 papers I wrote on this very subject. When the first Superman movie debuted, there were a few incidents of kids jumping out of windows with trashbags on their backs. Parents were outraged and demanded the movie or comics get pulled. Thankfully, the easily panicked parents were denied their requests because their kids were simply not understanding the reality that Superman is made up.
We know this logic is outdated, but we still see it prevalent today.
To be honest, I highly doubt that video games effect people enough to make them want to replicate what they do in the gaming world.
If those people are influenced easily enough that they would go steal a car in real life simply because they can do it in GTA, then those people shouldn't be playing games in the first place. Moreover, these people may need professional help.
I think if anything, games are used as a sort of scapegoat.