Alex Tabarrok has an insightful post about how closeness and severity affect the perception of torture. Read it all, but here's his conclusion:
The theory has interesting lessons for entrepreneurs of social change. Suppose you want to change a policy such as prisoner abuse (e.g. Abu Ghraib) or no-knock police raids or the war on drugs or even tax policy. Convincing people that the abuse is grave may increase their belief that the victim is guilty. Instead, you want to do one of two things. Among the patriotic you may want to sell the problem as a minor problem that We Can Fix - making them feel good about both the we and the fixing. Or, you may want to create distance - The problem is bad and THEY are the cause. People in the North, for example, became more concerned about slavery once the US became us and them.
I think research in moral reasoning is important because understanding why good people do evil things is more important than understanding why evil people do evil things.
It's very interesting to consider whether there are really any "good" people in any objective sense. Within the torture context the experiment that Alex describes demonstrates that each participant believes that he is the good guy, even if they think that someone else is acting evil. Christianity resolves this problem by asserting that there is an absolute standard of right and wrong, but absent God is there a humanistic way to examine "why good people do evil things"? Or is it more meaningful to simply ask "why do some people do things I don't like?"