"Thou shalt not extinguish thine anger, but shall master it,
that thy conscience may not be blunted by adjustment
to wrong causes." -The Dutch Ten Commandments to Foil the Nazis
Norm Geras over at Normblog answers the question about why naturally good people occasionally do bad things. His answer is that people aren't naturally good, but have potentialities for good and evil across all of their behavior. I'm not sure Norm would recognize it, but that's a pretty classic Calvinist definition of total depravity: there's no part of life where people do, or can, act from unmixed motives.