Most of us would agree that it's wrong to bludgeon someone with a baseball bat and take their car. Yet many of us take joy from simulating that act in a video game. This strikes me as wrong.
Here's a two premise argument:
(P1) It is wrong to commit unnecessary violence
(P2) It is wrong to take joy from watching or simulating wrong actions
(C1) So, it is wrong to take joy from watching or simulating unnecessary violence
Some clarification of the first premise is in order. Let's let unnecessary violence be any act intended to harm a person that is not a means to preventing greater harm or providing benefit proportional to the harm intended. It may wall be that it is wrong to commit even violence aimed as preventing greater harm or providing benefit, but I need only the weaker claim that it is wrong when it is not so aimed. I take it that this weaker claim needs no defense.
The second premise is less obviously true. To motivate your intuitions, consider the following situation:
Robby is a dedicated roboticist by day, working to build robotic aides for children's hospitals. He loves children and would never harm a child. In the evening, Robby returns home and, to relax, goes down to tinker in his basement workshop. Descending the stairs, he sees Roberta, a stunningly realistic robotic child that he has made. Roberta greets Robby with a smile and a wave and Robby, smiling back, takes up a crowbar and begins bashing Roberta in the legs. Roberta, being well-designed, reacts like a child would, adding to Robby's enjoyment. After a refreshing session with Roberta, Robby rebuilds his toy and retires for the evening.
I contend that the pleasure Robby takes in his basement is monstrous. It is not monstrous because it harms Roberta, for Roberta is a mere automaton; Roberta can feel nothing, has no interests, no desires, no goals. Roberta is incapable of being truly harmed.
Following Kant, you might think that Robby's actions are wrong because they pose an indirect harm to himself or others:
If a man shoots his dog because the animal is no longer capable of service, he does not fail in his duty to the dog, for the dog cannot judge, but his act is inhuman and damages in himself that humanity which it is his duty to show towards mankind. If he is not to stifle his human feelings, he must practice kindness towards animals, for he who is cruel to animals becomes hard also in his dealings with men. (1997, 212)
Replace "dog" with "extremely realistic robot" and Kant's reasoning applies to our case. But why should an act that does not harm a person be "inhuman" and damage in the actor "that humanity which it is his duty to show towards mankind" unless it is ill-fitting somehow? Even if we take the Kantian approach, we must admit that taking pleasure in simulated violence is to show disrespect to humanity or, what is the same for Kant, personhood.
Perhaps one would skip over Kant's claim that harming animals harms ourselves and, instead, jump to his claim that "he who is cruel to [extremely realistic robots] becomes hard also in his dealings with men." The problem with Robby's actions is that it makes him more likely to harm people. Maybe torturing Roberta just won't be enough for him at some point and he'll want to try it out on an actual child. His action is wrong because it makes that step more likely.
If this is right, then it is not (P2) but rather the weaker claim...
(P2*) It is wrong to take actions that make one more likely to do wrong
...that our case supports. (P2*), however, is not strong enough, by itself or with (P1), to get us (C1). What would be needed would be empirical research supporting the claim that taking joy in simulated unnecessary violence makes one more likely to carry out unnecessary violence. Perhaps the research would support this connection and perhaps it would not.
I think that the strength of the argument is not, however, contingent on the research. Even if we stipulate that, because of his psychological make-up, Robby's actions in his basement make him no more likely to harm a person, we'd still find his actions reprehensible...or so it seems to me. I'd be interested in hearing your intuitions on the case.
The upshot of this argument is significant. Simulated violence pervades out culture. We watch it on television, we enact it in video and table-top games, we read of it in our novels. Children make toy guns and pretend to shoot strangers. If the argument above is sound, this is all wrong.