He spent his time as a guest of the US government and saw how it really is.
This is important. He’s right:
If it is not the purpose of the entire post-trial penal apparatus, after punitive and deterrent purposes have been served, to encourage blameless and successful subsequent behaviour, then they have no legitimate purpose. If it is not now in the ethos of our civilization to adjudicate alleged misconduct, sentence in a manner that tempers justice with mercy and conclude at the satisfactory end of the sentence that the convicted person has expiated his offence and is entitled to a fresh start, then every man, woman and child in our society is at risk of the terrors of uncivilized places. If we do not salute and take comfort from reformed personalities and successfully relaunched careers, we are, as a society, complicit in an odious and primitive coarsening of life.