Sexual misconduct stems deep, deep in the subconsciousness, and once it is rooted, it can be hard to trace back. Therapy can definately help uncover those roots, though to a certain extent. One would have to break down the entire psyche and reconstruct it. That's not easy at all, even with the best of help.
Still, I've read cases of sex offenders (including children) who, with the appropriate help, managed to turn themselves around (though to what degree, we cannot tell). It largely depends on the individual and how willing he is to understand himself, and help himself.