I've got this great quote in my head, but I can't find the book it came from online. If it weren't for the fact I was sure I didn't, I might think I dreamed it myself. "Good will on occasion do evil things, but evil will always try to tell you that it's good." or "Good will sometimes do evil things" or something of that nature. I know the last part's right, and the fact that I can't remember where I got it is bugging me. I wanna say that it's either Inheritance Cycle, Tamora Pierce (which of her novels, I couldn't tell you), or Sherrilyn Kenyon, just because those are the books I've read where a conversation of this sort might have happened, but I remember reading a few new authors I've since forgotten around the time I read this for the first time.
It sounds familiar, though I can't cite the source. Similar quote might be: “People who claim that they're evil are usually no worse than the rest of us... It's people who claim that they're good, or any way better than the rest of us, that you have to be wary of.” ― Gregory Maguire, Wicked: The Life and Times of the Wicked Witch of the West Hth