Things that live by night live outside the realm of 'normal'...

Things that live by night live outside the realm of 'normal' time and so suggest living outside the realm of good and evil, since we have moralistic feelings about time. Chauvinistic about our human need to wake by day and sleep by night, we come to associate night dwellers with people up to no good at a time when they have the jump on the rest of us and are defying nature, defying their circadian rhythms.