The Chayav Misaa discussion above is moot. Younger than age 20 is not considered a bar onshin, and sentences cannot be imnplemented.
The reference to teshuvah is also completely irrelevant. That entire subject is not to be addressed by other people. It is solely bein odom laMakom. If HKB”H is mocheil a molester, goody gumdrops for him. We are obligated to insure that our children are safe. Since there is no known treatment that can reliably render a molester 100% safe, we must take whatever precautions are needed. And halacha is not an impediment to this. On the contrary, Sh”A refers often to taking measures to protect the integrity and safety of the tzibbur.
PBA – You concluded that this 15 year old perpetrator was once a victim. You can’t possibly know that. The statistics of victims becoming molesters themselves are not overwhelming, though we can understand the process of victim coping with his own trauma by becoming the perp. The statistic is of a noticeable percentage of convicted molesters reporting a history of victimization. Though noticeable, the numbers are not dramatic. However, you went an extra step in suggesting that the victims will one day become perpetrators. That is rather unjust, to put it lightly. In fact, a very tiny percentage of victims ever do this. Pronouncing them perpetrators is revictimizing them. Unfair, dishonest, and intellectually repulsive.