Would you consider these people so dangerous that you would personally build a small concrete box and forcibly keep them inside for many hours a day for the rest of their lives? Or, is that how you would treat your children if they committed some minor, nonviolent, kinda-maybe-bad act?
No reasonable person would - the moral decision above is clear. Would you pay for someone else to do this?
We are brothers and sisters in humanity, and we elect people who write these laws and treat fellow people like this (and/or refuse to reform the US Sentencing Commission). We are to blame.