Ok, for fuck's sake. Here's the low-down (not really a pun, but still...)
The Nature part is simple, guys want to put their dicks in holes cause of the urges, that's pretty self-explanitory, isn't it? And as far as the nurture goes, it better be pretty fucking pretentious of the nurturer to make sure the child represses all of their sexual urges towards little kids after they grow up. If the child themselves are molested or raped, it might become repressed and by that they would act compulsively reliving the same heightened sensations they recall from their childhood and thereby reaffirming their erotic nostalgic memories. Oh, but what happens to those that don't repress? oohh...good question. My guess, you'll hear about them being 50+ years old and having a 20 year old wife, but only after the fact will we ever really find out. Hehehe..."No one can stop me now, cause I don't care anymore..." -Nine Inch Nails