People can handle evil characters(for the most part--usually they twist their behavior and water it down) but people really can't handle good characters that lose their head or lose themselves and have a moment of fallen grace. Fandom has shown this time and time again. They really look at them as worse than the initial evil.
related but tangential. there's a really strong unexamined belief throughout a lot of fandom -- and population outside of fandom, but we're talking about fandom here -- that what you do and say during your worst moments is who you really are.
And the assumptions underlying this, more or less, break down to:
- Everybody is secretly bad deep down. They're born that way (no, this is not original sin, wdym, it's just an Honest and Realistic assessment of human nature!) and have to be taught to cover it up through childhood with facades of politeness. Everybody is lying all the time by pretending to be better or nicer than they really are, and this facade takes active effort to maintain. When the effort drops and the facade slips, the true underlying rottenness shows through.
- All actions taken are rational and reasoned, at all times. Lying is always a deliberate, purposeful action meant to advance a person's aims and goals. There is never any reason to lie except to make yourself look good. Therefore, any good or nice statement or action may be a lie, but any bad or harmful statement or action must be true.
Ergo: anything a person (or a character) says or does when in states of emotional extremity, overwhelming grief, incapacitating pain, exhaustion, illness, head injury, is Peeling Back the Facade of Goodness to reveal the True Rottenness Underneath. So not only are you actually as evil as the evil character, you're also a liar.
This is, of course, utter nonsense. But an amazing number of people seem to believe it.