Virtual violence is not violence; but virtual violation is violation... The disanalogy between violence and sex arises from the fact that violence is a physical activity whereas sex is a physically expressible mental activity.
I'm not sure about this. It seems like there's also a mental component to violence, that could potentially be separated from its typical physical expression. This should capture the kind of violation that also occurs through, say, verbal bullying. Since it's possible for virtual (non-sexual) violence to still be violating, the posited disanalogy seems a bit artificial.
What we really need, I think, is to disambiguate two senses of "virtual violation":
(1) A real violation that occurs within a simulated, or 'virtual', setting.
(2) A merely simulated/'virtual' violation.
The distinction generalizes. Consider the example of "virtual bullying". In the first case, one could genuinely bully a fellow game-player whilst inside the game, if the bully intended to use the game to (emotionally) hurt the other player. But in the second case, I might merely simulate it, i.e. role-play having my character "hassle" another, whose real-life player understands that no real animosity is meant. In the second case, but not the first, it's just a game.
Similarly, two people might have (real) sexual relations within a virtual world, or they might merely simulate it -- depending (at least in part) on their respective intentions, I suppose.
One can imagine a game, then, where "virtual rape" occurs purely in the second sense. Perhaps it's part of the rules of the game that if you lose to the boss monster, it will "rape" and "kill" your avatar. If that's a normal part of the game, I assume no-one would feel violated by it. (Especially if the boss monster is just a computer program, rather than another player. But even in the latter case. Real-world sexual roleplaying provides a vivid example of this -- handcuffs, anyone?)
The distinction, I suppose, concerns whether real consent is given for one's avatar to be acted upon against its (merely virtual/represented) "consent". By playing a game, one gives a sort of global implicit consent to all the normal happenings -- getting killed by monsters, and so forth. (Even though in the "local" moment of a game you try your best to survive, of course!) So we can also imagine cases where a player gives a similar global consent for their avatar to be virtually "raped" in certain legitimate circumstances. The problem with the Second Life virtual rapes, of course, is that no such global consent was given. Virtual rape is not a "normal" or legitimate kind of interaction within the world of Second Life; it is not what the players signed up for. So when their avatars are violated in these ways, so -- to a degree -- is the player.
The virtual violation was a real violation, because not only was virtual consent missing -- so was real consent. This general principle applies to non-sexual virtual interactions too, e.g. virtual bullying. The difference we see between this and normal cases of "virtual murder" isn't so much in the type of act, but in the type of consent.