Not everyone who smokes will die a horrible death from lung cancer and/or heart disease.
Not everyone who drinks and drives will kill people in car crashes.
Not every instance of sexual activity between adults and minors will result in intense emotional damage.
However, the probability of harm involved in the above activities is so great that society does have the obligation of pre-emptive sanction, or at least for the last two where the harm is towards others rather than one's self. I think the distinction is important philosophically, because attaching metaphysical certainty of harm actually undercuts the rational case for banning or discouraging certain activities which have a high probability but not an absolute certainty of harm.
The bottom line here is minors are not making choices when adults are involved in pediphilia. End of story.