I don't pretend to have enough information to debate this, but most people would point to the reality that many criminals who are let back into society become repeat offenders (whether that's because of the situation we put them in - or simply because they are a moronic POS who don't deserve to be part of society). What % become repeat offenders? I don't know, but what % is too much? If there are 100 registered sex offenders and only 15% repeat - that's 15 more kids that are molested by some f***ing wacko. IMO, that's 15 more than we should ever allow....especially when the "upside" is to simply let 85 registered sex offenders back into society...
I'd say about 2 years ago now, a registered child molester, who's been convinced multiple times, who apparently said in court that if set free that he would molest again, was relocated from Saskatchewan to rural Ontario - some 15-20 minutes from my house. It's f***ing scary and creepy.