Quick question for clarification: are those 'dozerns of people that don't' also pedophiles?
If they never commit an
act of pedophilia, does it matter? They'd be behaviorally identical to a non-pedophile. Lump hebephilia and ephebophilia in there too, to be fair -- use the broader term instead of the clinical, to fit better with general public understanding of the behavior... though that understanding goes a hell of a lot further than the clinical definition.
We're talking essentially about imprisoning people for life for thought-crime, on the off chance they act on that thought -- and that in the face of the fact that a great deal of those guilty of that thought crime never act on it.
Even without that. You're still going to have a significant fraction of those dozens who
aren't. The position we're discussing is saying that it's acceptable that a dozen innocent people be imprisoned in order to prevent the one who isn't from victimizing someone. Or rather, that it's desirable to victimize many to an (arguably) lesser degree to prevent a smaller number of greater victimizations.
Or, being fair, the position in question is talking about magical utopia world with 100% accuracy, no false positives, and no corruption. We don't have that, and can't for many years to come, if ever.
I can appreciate the sentiment -- treat the cause, not the symptom -- but we just don't have the technology and methodology to
do that, and won't for a damn long time. Until then, our way of treating the cause is close enough to as bad as the symptom you can't really morally weigh which is the better situation.