Involuntary in-patient psych care is different than prison because it is focused on improving someone's life, managing a potentially dangerous condition, etc. They (should be) a hopeful place, a place of healing. They don't always live up to that, of course, but at least the objectives are correct.

Prisons are not places of rehabilitation in the US, and a person who is suffering from a severe mental illness is likely to suffer profound abuse in prison.

Involuntary psychiatric facilities also have a rather checkered past when it comes to human rights, to put it mildly.

Anywhere you hold someone against their will eventually becomes fraught, no matter what the stated purpose of the facility is.

True, though I'd much rather have a well funded, competently run mental health facility than a well funded, competently run prison.

There's an extremely wide gamut of potential answers to this question. "Either we lock them up and throw away the key in a violent retributive system or we let them roam the streets free of all social constraint" is a false dilemma.

At any rate, it's not necessary to pick a specific answer from the massive pile of alternative approaches tried, theorized, and developed in modern history to say that this one thing that is done in the US right now is clearly not the right answer.

What should ideally be happening would be rehabilitating them in an environment that doesn't constantly reinforce the idea that they're subhuman garbage.