It is odd that you go from "don't imprison non-violent offenders" straight to "don't punish non violent offenders".
There's a bunch of stuff that we can do that is cheaper than prison, and better at stopping people from committing more crime. Restorative justice programmes are pretty good.
> The suggestion that the threat of imprisonment does not act as a deterrent to criminal activity is absurd.
Why are you not a thief? Is it because you're afraid of prison, or is it because you know that stealing is wrong?
The rate of recidivism is pretty high, the US imprisons so many people yet still has crime.
> Do you really not see "I'm here because I screwed up. I probably should try to not screw up in the future." going through the mind of prisoners as they sit in their cells?
But it doesn't. Really, it doesn't. People pass the blame onto others. Prisoners may well think "I screwed up by getting caught. I probably should try harder not to get caught in future".