Ross Douthat, writing about Penn State in the NYT:
Bad and mediocre people are tempted to sin by their own habitual weaknesses. The earlier lies or thefts or adulteries make the next one that much easier to contemplate. Having already cut so many corners, the thinking goes, what’s one more here or there? Why even aspire to virtues that you probably won’t achieve, when it’s easier to remain the sinner that you already know yourself to be?
But good people, heroic people, are led into temptation by their very goodness — by the illusion, common to those who have done important deeds, that they have higher responsibilities than the ordinary run of humankind. It’s precisely in the service to these supposed higher responsibilities that they often let more basic ones slip away.