IMO I believe it's so hard if not impossible to treat because many are only sexually aroused by children, they carefully select, cull them from the herd and groom children. Many actually believe the child is capable of consent and they do not believe they are hurting children. They claim to "love them"
That leads me to believe, at least for some, it is a sexual orientation all it's own. I'm straight and all the therapy in the world can't change that, same for homosexuals no therapy can change it. IMO it's hard wired like pedophilia.
Pedos can't be changed because they do not think they are doing anything wrong.
They are just like Ariel Castro. No clue about their behavior.
I imagine it to be an orientation as well. Which is why it can't be changed. I have read testimonials from homosexuals who were put through religiously sponsored and designed therapy programs, how they came to be resigned to the fact that they could never change how they felt, they would (due to personal religious beliefs) resist acting upon their native sexual desire. It sounds like a living hell.
In the case of pedophiles, if we think of it as an orientation, that, to me helps explain why it is not possible to rehabilitate. I know that my sexual orientation is fixed, it isn't oing to change.
Now what I'd be interested in knowing, and I imagine it's a tough question to answer: are there pedophiles out there, who are denying their desires? Good upstanding citizens who don't commit crimes on child victims, because their will to do the right thing won't allow them to, even though the sexual attraction is strong.
Am I making sense? The sexual attraction is only a problem if it is acted upon. In the case of consenting adults, acting upon the sexual attraction is not a problem ever, regardless of the action taken. (What you do at home in private is 100% okay, as long as all parties are agreeable).
The problem comes in when there are victims.
Another example would be people who are aroused by exposing themselves. Obviously, we can't allow that, because their actions effect others.
But my point is that if pedophilia is sometimes hardwired, like an orientation, that would certainly explain why it can't be fixed. And furthermore it's possible that there are people out there who are fighting that attraction with all their might because their morality not to claim victims overpowers their desires. The trouble is, not all of them fight it.
I think in other cases pedophilia is a response to environment. A child is sexually abused, and they grow up to sexually abuse also, because they've come to associate sex with a certain set of circumstances, but even that is hard to tease out, given that incest is as common as it is, it would have to be studied carefully to determine what fraction is nature and what fraction is nurture.