so, if i don't believe in retribution, and i don't believe in deterrence, why would i put anybody in jail in the first place?

i mostly wouldn't.

i do think that there is a valid justification for incarceration, and that is to protect the community. the logic here is that the rights of the community to protect itself overpower the rights of the individual to freedom. now, this is subject to due process and habeas corpus and all that kind of stuff, but, at the end of day the only reason i'm going to support incarceration at all is if i think that this person being incarcerated poses a threat to the people around it. and, there are some twists to this. for example, i would interpret "not criminally responsible" as a life sentence, rather than an acquittal, because the issue isn't whether you disobeyed the king but whether you're a threat to reoffend. further, it would necessarily follow that detention facilities should function more like hospitals than jails, because the people being housed in them are there precisely because they can't be reintegrated due to some kind of mental incapacity. if there's any way out at all, the system should accommodate for it.

given that i would argue that the purpose of a jail is to prevent the people in it from further harming the community, i don't see any kind of moral problem with telling these people they can't vote; they're being held in quarantine, they're being cast out, they're there explicitly because they're being excluded.

and, the real exercise of democracy here is in the community exercising it's right to exclude those that might harm it.

bernie's old enough to make his own choices and choose his own battles. if he wants to go down in flames on this, it's his choice, but he's wrong and should step back from it.