I can understand the outrage over this decision but I hope that when tempers cool a bit someone will consider the points that the judge made:
Lengthy incarcerations are expensive and don't seem particularly effective at altering behaviors anyway.
Letting someone out of prison after a long term of incarceration and making him register as a sex offender destroys any chance of his obtaining a decent job and being too busy working to re-offend; it only gives him a sentence of poverty, idleness, frustration, alcoholism, community scorn and other things not likely to lead to law abiding behavior.
I don't know if this defendant will re-offend or not. I think the sentence is a bit too lenient, but it will be an interesting experiment. Certainly the judge is correct in his statement that punishment does not seem to work.