Well as long as one keeps their mental rot within themselves, I don't see how its anyone's business. Thought policing is much more dangerous for society (and the children) than someone's private nonsense.
Understanding that people deal with some dysfunction or the other is the cost of living in a free society. Everyone struggles with some inner demons. Some much more than others. But we largely trust that they can keep these impulses in control. I don't advocate at all that we must empathise with those having this sort of disorder but we must allow people to deal with these issues privately.
Better, more vigilant policing is the answer. The impulse to stop crime from happening at the point it takes root in someone's mind is just the road to the worst kind of tyranny.