I typed a huge long post trying to summarise the chapters in the book (Monsters and Men by Bob Long and DCI Bob McLachlan) about the Wolvercote Clinic, where intensive work is/was being done with sex offenders, but I accidentally caught some key or other and shut down the whole internet 
Essentially the clinic is/was attempting to get the offenders to examine their behaviour and teach them techniques to control their urges to offend. The clinic's manager was very keen to point out that the purpose of the work was child protection.
My instinct is that sex offenders (of any stripe but especially paedophiles) are the most difficult, if not impossible, to rehabilitate. It's such abhorrent behaviour to most people, that to cross the line must indicate something fundamentally "wrong" in the psychological makeup of the offender.
The Wolvercote did seem to be doing really valuable work, I do wonder sometimes that it might be a good thing if people could self-refer to services like that, eg someone who is attracted to children but recognises that it would be wrong to act on that desire could go for some help and treatment.
In an ideal world I'd like to lock up sex offenders and throw away the key, but realistically rehabilitation is the thing to aim for.
The book is out of print (and a horrible read) but it's very interesting. ISBN is 0-340-86213-0 if anyone wanted to try the library for it.