There are other ways to define evil though. Some people don't see evil as something that is social in natures; instead, they almost see "Evil" as having its own kind of power and presense and reality. To such individuals, you don't "break the social order", you "succumb to Evil". They basically see the rules that Sangwa speaks of as natural or God-gievn, and therefore Evil is some sort of real life energy and force, and not just something that happens when we define some else a certain way because they live by different rules than we do.
Those people are what I meant when I said "mentally crippled." Maybe I should have referred to them as "socially severed." One often results of the other, as in normal conditions people are susceptible to social behaviour.
I believe that being certain that you are bad or wrong by nature, without provocation or need, is a psychosis. Normal people will usually find a reason to why they do things, or at least some kind of excuse.
The definition I gave is the objective one. The subjectiveness of the concept is the part where it deals with "moral" values. Moral values are traits of society and character.
Therefore we are still able to conclude what I previously did: we need to approach a more realistic view of "evil" and "good" in PS, as it is supposed to be a realistic setting. Instead of looking at those as sides to take on a battle, we should make sure people see them for what they usually are: common moral issues.