people who have idea's about young children have NO place ANYWHERE in society.
Do you have a deserted island we can put these people on?
Yes, its a heinous crime, but what do we do with him now? Or after he is released from whatever incarceration he is sentenced to? His current (or last) profession didn't put him in contact with children. And once his co-workers know what he's been up to, they can keep an eye on him. He'll probably be in some work release program for the foreseeable future, checking in with the local authorities and perhaps wearing a GPS tracking device.
But if you just kick him out on the street, he's got time on his hands and the possibility of moving into a career or new circle of acquaintances that are not aware of his past.
Unless you've got that island ready, he will remain a part of society. Sure, you could give him a bus ticket to the next town. But they wouldn't be too happy about that. And the buses run in both directions.