There was a documentary on just this last week, looking at reasons why some people are attracted to children instead of being protective of them.
In a number of offenders their brains were wired differently, sending signals to the sexual area instead of how normal adults respond to children.
I wish I'd paid more attention to the documentary, but the underlying message was that paedophiles are wired to be attracted to children. I think it also suggested that without hormone treatment, they were unlikely to be able to change.
I wonder if this is as much a desire created by nature as all other sexual preferences.