Unfortunately, there are also mentally unbalanced people who allege really wild fantasies. Sorting out the real from the schizo-affectively imagined fantasy can get tricky. If someone came forward, say, with allegations like the ones about Shanley and claimed that a priest you know well, like, and think is fine, did them, you tend not to believe that kind of thing. That it is possible for some individuals to be so compartmentalized that they can do outrageous things and then resume a routine, mundane, appearance of normality, makes it all the more confusing.
I will guess that part of the whole sex abuse problem has something to do with the fact that very wholesome, innocent, orthodox people have trouble realizing that such outrageous and profane conduct does take place. Evil can be bizarre.