I think it probably is.
Prisons are pretty inhumane: this has been recognized in the modern era by people as disperate as Johnny Cash and Eugene Debs[0] (and many others besides).
The cloak of "rehabilitation" or "correction" is really just a way of making punishment more paletable -- and as others in the thread have commented, that is actually what many people (in the US and Britain certainly) believe prisons are for, and ought to be for. But punishment doesn't improve society: recitivism rates remain very high even with very brutal criminal justice systems, and obviously don't deter. Even the "Bloody Code" in the 19th century in the UK didn't work, otherwise crime would have died out.
The causes of crime are various and complex. If we want to reduce crime and bring about justice and security for everyone, we need to address those causes. And as Debs wrote about rather eloquently after spending time in prison, all the American system has done for hundreds of years, by and large, is take people in desperate circumstances and make those circumstances even more desperate. It essentially exacerbates the causes of crime in countless instances.
Thus the fight for real justice and real peace has to be the fight not just on behalf of victims, but on the perpatrators as well. It prevents more victims, for one. But Christian duty, and Christian compassion, also demands caring attention to everyone, even people that have done truly terrible things. This isn't easy, or even pleasant, but that's one of the real radical roots of Christianity.
That struggle for justice and peace isn't as simple as "open the gates of the prisons, and let people do what they want." A lot of people would try to reduce such an argument to that. It's a process, and a path, and taken seriously, we could find ourselves at the end of that path with a society that is fairer, happier, more peaceful, and which has no need of prisons.
(And as a further aside of personal interest, that question of radical Christianity and the very real attention to the precepts of the gospels was one of the things that led George Fox to found the Quaker movement, which was also for a long time considered insidiously radical, and violently surpressed: largely because the Quakers refused to swear oaths or participate in war. The Peace Testimony of the Quakers -- also often treated in reductive terms along the lines of "oh, so you don't fight to defend anyone then" -- is pretty powerful stuff, that acknowledges the complexities of conflict and violence[1], but also the causes of conflict and violence, and seeks to end violence by putting an end to the causes of it[2].)
[0]: https://archive.org/details/wallsbars00debs
At some point I reread Isaiah 61:1, "...to proclaim liberty to the captives, and the opening of the prison to those who are bound...," and it's been bugging me ever since that prison is, as far as I know, not a concept in the Judeo-Christian worldview. Isaiah doesn't want to proclaim liberty to the unjustly captive and release to the unjustly imprisoned; he's proclaiming release to everyone.
All the examples of people going to prison in the Bible that I can think of - Joseph in Egypt, Daniel in Babylon, John the Baptist in Judea, Paul and Silas in Philippi, etc. - are of "good guys" being thrown in prison by "bad guy" governments. I can't think of an example where God says to build a prison, or where a follower of God puts someone in prison, and the Bible says they did a good thing. (Maybe I'm forgetting something, though; I'd appreciate correction here.)
For all that Western culture seems to be proud of our Judeo-Christian morality, did we inherit this one keystone of our whole thing from pagan concepts of how to run a justice system?
And is it my religious duty as a Christian to fight for release for all the prisoners?