Since most of us were kids, we've heard the same damn things about violence in video games; that it's wrong, evil, promotes violence on Earth, shapes our minds into killers, ect. There have been numerous studies that look for evidence to link violence in games to violence in real life, and they have all come up wanting. Apparently people have been getting pissed over the violence in Bioshock: Infinite - which, if you've played, is entirely necessary in the context of the game. Instead of a witchhunt to find the causal link from virtual to real violence let's make the whole point moot.
In real life, any rational person knows that violence against another person is wrong, (except in self-defense ect.). We all exist in reality, and human life is of the highest value to us. From reality, we draw our ethics and code of values - all fundamentally based in what is real.
Now lets look at games. Games are virtual worlds, or virtual realities - each with their own plots and worlds governed by the programmers (not reality).
Since the laws of the virtual world are different from our own, the player learns these laws and develops their own play styles accordingly.
In reality, actions have consequences. Yet when the player stops the game and turns off the virtual reality, all of the consequences of actions taken in the game stay in the game. Stealing, killing, vandalism, robbery, all of these actions and their consequences end the moment the game is turned off. In other words, the game is not reality. Since the game is not real, "life" in the game has no value in reality, no real value. In truth, there is no real life in virtual reality, only virtual life. As such it has a value only to a virtual existent - the protagonist that the human player is controlling. To the player himself, virtual life and violence is meaningless because it is unreal.
To the character being controlled by the player, if that entity could have any thoughts of his own (or free will), the life in the virtual reality would have meaning to him. Yet his nature as the player-controlled character denies this possibility.
As a player, virtual life has no value. The only role of reality's ethics in the virtual world is then roleplay - assuming the identity of the character. The purpose is the plot, which many times sets violence as both necessary and good in terms of the virtual world. Either way, the morality of video games is irrelevant in its very nature as being virtual. The player can pretend the virtual reality is real, and thus "play" morality - yet myself like many other gamers would prefer to simply "play".