You don't think that being molested by your grandfather might have something to do with replaying that molestation obsessively throughout your life, and trying to come up with hypotheticals in which it can actually be ok?

I'm just operating at the preponderance of evidence level here, and it seems far more likely to be to case that extreme childhood sexual caused the extreme sexual deviation. Do your P(A|B) work here, it's not hard, given the small probability of both of those things.