Jonathan Haidt wrote a wonderful book, <The Righteous Mind>.
I think it's very relevant to pedophilia. It's been a few years since I read it, but as I remember it he sketches two kinds of morality. The liberal morality is that everything's OK if no one is harmed. The conservative morality is that some things are just plain wrong.
One way to diagnose which kind of person you are is a set of examples.
1. A man's pet dog is hit by a car and killed. Having heard that dog is tasty, he decides to cook and eat it.
2. An adult brother and sister decide they want to have sex just once, to try it out, so in great secrecy and with lots of contraceptive protection, they do.
3. A man purchases a dead chicken and then has sex with it.
For most of us, they all give rise to a "yuck" reaction. But after the liberal thinks about it a while, he'll grumble and then say that he can't see why it's immoral. The conservative still thinks they're all immoral.
Now, you won't be surprised to see me raise case 4, which is not in the book:
4. A man is sexually attracted to young girls. He knows he will never act inappropriately with a real girl. But he likes to find pictures of such girls online in bathing suits happily playing, and he masturbates while looking at them.
How does that sound to you? (Perhaps you don't believe that he will never act inappropriately with a real girl -- if so, maybe imagine a man in prison for life without parole?). Is it worse than eating your pet dog who was hit by a car?
5. A gay man is really turned on by a straight coworker who he knows does not find him at all attractive. At home at night, he masturbates to a picture of the man at a pool party, imagining having anal sex with him.
This might or might not give rise to any "ick" factor in you, but there is perhaps another consideration rising. This gay man isn't just fantasizing about the coworker on a lark -- he is gay, and his sexual nature is to be attracted to men. If you're like me, you feel a bit of an obligation to not feel bad about this. It has no appeal to me personally, but I feel like I owe it to this gay man to accept his sexual fantasy. Perhaps he's in the unfortunate position that due to his particular tastes he can never have a real partner.
Now let's return to case 4, the man masturbating to pictures of girls in bathing suits. Can you find it in yourself to get some of that same feeling of sympathy? This attraction is central to his sexuality. He didn't choose it and he can't change it. That masturbation is the closest he can ever come to sexual satisfaction.
And for the next question, are you worried about immorality from thinking about the girls without their permission? Are you worried about the straight man in the same way?
I know some social conservatives have had to face a head-on collision between their convictions and the reality that their son or daughter is gay. Some of them accept their child; some will accept that the sex that he or she engages in is not wrong. Could any of them accept with equanimity the idea that their pedophile son will masturbate to fantasies about children?
And here's an extra credit problem: Suppose your pedophile son hates his attraction and whenever he finishes a guilty bout of masturbating while thinking of a child, he wants to kill himself. Could you find it in yourself to try gently convincing him that his celibate attraction isn't such a bad thing?