Francis' speech is plainly the moralising of a fantasist. In every country there is a small, but significant number of people who represent a long term danger to the general population. I can think of obvious examples such as terrorists, serial murderers, large scale organised crime lords, war criminals and predatory paedophiles. If capital punishment is abandoned, as it has been in England since the 1960s, the only practical alternative is permanent detention, or conceivably some form of continuous observation so restrictive that it is akin to permanent imprisonment.
Broadmoor Hospital is about twenty miles from my home. Just about every inmate is there because of truly heinous crimes. Our long term and high security prisons contain a considerable number of "sane" criminals whom you would not want to meet in a dark alley, or anywhere else for that matter. Are these seriously going to be released regardless of the threat to public safety? It speaks volumes about the warped morality of Francis that he says almost nothing about the safety of children or other innocent members of the community, or about those who have been murdered by released murderers.
The Church has too much of a vested interest here. Obviously the paedophile priests are among those looking for mercy at all costs. And the reference elsewhere in his speech to treating elderly criminals gently smells too much of the anxieties of those clergy whose vile crimes catch up with them decades later.