Nifft said:
Trouble is, the black-and-white morality of D&D is a staple of the genre.
I'm not arguing this, but I don't think that it's entirely true, either. I don't believe D&D has a black-and-white morality. I think they have an illusion of black-and-white morality that most people choose to believe.
Here's what I mean by this ... and I'll refrain from using real life examples to try and keep it from getting into a debate. But, if the morality of D&D were black and white, then we should be able to make statements like killing, lying, cheating, rape, disrespect for life, etc are all wrong.
But the truth is, D&D's main staple is the combat system. In fact, unless you take the Justicar PrC class (or burn a feat) it is actually a system that penalizes anyone wishing to do nonlethal damage to their opponents. In truth, the game designers premise is that combat would be lethal. In a black-and-white morality I personally think that would make most of the adventures "black" by definition and not "white." [I fully assert that this is my own opinion and it is based on the opinion that killing demonstrates a lack of respect for life - even if the life is evil or attempting to accomplish evil things.]
To me, that means that D&D's assumed game morality is either circumstantial (meaning that its okay to kill evil in most circumstances but not okay to kill good in most circumstances) or that at the very least it isn't black and white. I think we have an illusion of black-and-white morality because the game designers paint it that way ... but the reality is that the illusion is really quite circumstantial.
Like I said, not trying to argue it ... just illustrate that D&D morality is more circumstantial than anything else.
Back to the op's initial question ... the BBEGs in my campaigns are often members of the PC races gone bad (or undead and evil outsiders).