I'll say what I've always said about violence in media.
Video games, and every other piece of media for that matter, can have effects on people, positive or negative. To say that there is absolutely no effect on people who play violent games, watch violent movies, read violent books, etc... is ludicrous because we so readily accept that they can have a profound effect on us emotionally already. Is it so hard to believe that video games may cause some short-term aggression in people when we readily accept that they can make us laugh, cry, feel releif, all sorts of emotions, and just angry in general? Video games and other media are usually not the causes of negative social behavior but rather an outlet, and in fact most of the studies that are shown on the Escapist from both sides state this fact.
There was an article on the Escapist about a study on violence in video games, and for the most part the study itself was fairly neutral. The article, however, was wrought with bias and self-inserted opinion, bullshit ad homeniem against the scientist, and overall so much crap that it was a disgrace to The Escapist and journalism in general. The studies on both sides or the scenario are nowhere near as biased or partisan as people might think, most of them agree that there is some short-term effect with video games as most media tend to have.
Just because it's fantasy does not mean that it can't have an effect, whether positive or negative, whatever the effect may be, and to say so discredits the very reason why we pursue these escapist mediums in the first place and their effects they have on us personally. This book [http://en.wikipedia.org/wiki/The_Bible] has influenced millions of people, for good or ill, throughout history. John Lennon's killer cited this book [http://en.wikipedia.org/wiki/Catcher_in_the_Rye] as an influence. Hell, this movie [http://en.wikipedia.org/wiki/The_Birth_of_a_Nation] influenced film itself despite it's racially charged subject matter. Media clearly has an affect on people, positive or negative. Nothing more, nothing less.