Even if we hold to a moral standard, we can still fall short of it. I am as influenced by emotion as any other human being, and can make flawed decisions.
Perhaps a key point to consider in this issue is how we define good and evil in our campaigns. For example, a very good guideline to what is good is to not do something to others that we would not wish done to ourselves. Looking at this as a possible guideline, evil can be perhaps looked at as either intentionally or through neglect causing harm.
For example, I would argue that someone who makes a profit on someone else's suffering (such as a slave owner) is committing an act that can be interprepted as evil. Mind you, the person may well have good and noble qualities. There can be conflicting impulses in a person which are sometimes never reconciled. (For example, Thomas Jefferson struggled with the contradiction between the philosophy "All men are created equal" and being a slave owner.)
As for evil, there can and perhaps should be many different types of evil in a campaign. Some may seem psychotic, others may be far more subtle. Indeed, many villains may try to hide their true natures behind a cloak of good deeds. (As a very simple example, in the comics Lex Luthor tries to portray himself as a good-hearted businessman and someone who does support charity. The good PR is good for business.)
In a campaign setting, different faiths and cultures may still be considered good but have different takes on the nature of good. I think trying to develop this can add to a campaign, and give players more to work with. Indeed, good people can be in conflict over difference of belief and how to approach a given situation.
I would like to see less ad hominem attacks. Also, maybe do the political debates over at
http://pub53.ezboard.com/bnutkinland in the Fighting Words forum.
I have a great deal of respect for the people on this thread, and wished I had more time to participate in it.