The Unforgivable Sin?

In most western nations, the penal system is designed to reform convicted criminals so that they can return to a productive life in society. In the USA, where we have two million people in prison and nine million on parole, a far greater percentage of our population than any other western democracy, prison terms are more likely to be used for a kind of social revenge than they are for reform. Sex crimes are typically considered to be the most heinous, but in a penal system bent on putting more people in prison for longer sentences, have we lost our way in imprisoning those who have not committed rape, assault, or even sexual harassment but who have viewed illegal pornography in their own homes? A teenager with the impulse control issues that often accompany autism or bi-polar disorders who watches child porn in private may not be "innocent" but is their crime on the scale of murder? If not, then why do we punish them more severely than we do murderers? Have they, somehow, committed the unforgivable sin?