I imagine you are absolutely correct about people having strong emotional reactions to rape and child pornography. In fact, much more so than murder, the mere mention of the other two crimes can cause an emotional reaction, whereas for most people, the murder needs to be of somebody they know to have the same level of emotional reaction.
On the other hand, within some games, death is a normal part of the game. In FPS style games, murder is the entire point. In this sense, our expectations are different in the game to in real life. But since rape and theft are not expected in most games we are taken aback and shocked if it happens. I wonder if murder might matter more in a game where death and murder are uncommon.
As for the technology, I'm not sure if you are familiar with the LambdaMOO case or the technology involved. As for me, my University used their own MOO based on the LambdaMOO as a tool to help teach their Computer Ethics course and I have had a character on the actual LambdaMOO in the past.
A MOO is basically a multi-person text-based adventure game. You can cause any text you like to appear on the screen of everybody currently connected if you know how. The rapist could cause the text:
Macgrrl slowly takes off her clothes.
to appear on the screen. This would (to most users) be completely indistinguishable from Macgrrl actually typing that. The technology is low but precisely because of that, the power of words became greater. Any player could completely alter the world as you (and everyone else) saw it. With current games, our power over the world is much less because the world is so much more complex. We can only do what the developers give us the ability to do. But this has not changed the emotional involvement (at least for some people). I think the emotional involvement comes more from the social interaction rather than the online persona. In the LambdaMOO case, the avatar was an extension of her real world self and had real friends, even if they were only ever contacted in a virtual setting. In that sense, WoW is unlikely to ever have this problem, but Second Life very well could or, as you said, Surrogates. The technology, however, I think is almost irrelevant. It's just the player's power over the world and other players that matters and the technology affects this.