It seems that there is a general rule in the moral universe which may be formulated “The higher, the more in danger”. The “average sensual man” who is sometimes unfaithful to his wife, sometimes tipsy, always a little selfish, now and then (within the law) a trip sharp in his deals, is certainly, by ordinary standards, a “lower” type than the man whose soul is filled with some great Cause, to which he will subordinate his appetites, his fortune, and even his safety. But it is out of the second man that something really fiendish can be made; an Inquisitor. “It is great men, potential saints, not little men, who become those who are readiest to kill for it”. For the supernatural, entering a human soul, opens to it new possibilities both of good and evil. From that point the road branches: one way to sanctity, love, humility, the other to spiritual pride, self-righteousness, persecuting zeal. And no way back to the mere humdrum virtues and vices of the unawakened soul. If the Divine call does not make us better, it will make us very much worse. Of all bad men religious bad men are the worst.
Reflections on the Psalms, C. S. Lewis, p. 146-7