When I was reading The Seven Biggest Dick Moves in the History of Gaming, I was struck by the number of people who are strongly motivated to cause misery to others [1], apparently for its own sake. I think the default assumption here is that the primary risk to ems is from errors in programming an AI, but cruelty from other ems, from silicon minds closely based on humans but not ems (is there a convenient term for this?) and from just plain organic humans strikes me as extremely likely.
We're talking about a species where a significant number of people feel better when they torture Sims. I don't think torturing Sims is of any moral importance, but it serves as an indicator about what people like to do. I also wonder how good a simulation has to be before torturing it does matter.
I find it hard to imagine a system where it's easy to upload people which has security so good that torturing copies wouldn't be feasible, but maybe I'm missing something.
[1] The article was also very funny. I point this out only because I feel a possibly excessive need to reassure readers that I have normal reactions.
I think that you raise a legitimate concern. I think that as opportunity for growth increases, it will be to people's advantage to rewire themselves to be more empathetic so that they can cooperate with one another more. So I think that people's enjoyment of torture will go down on average. But this doesn't entirely preclude the concern that you raise. I think that all that one can say is that while there's a good chance that there will be torture in the future if the human race survives, there will be a lot of counterbalancing ecstatic experiences. Whether the latter can balance out the former is in some measure a matter of perspective.