This premise is false. People have gotten along without the present distorted system of mass incarceration, not having a system of punishment doesn't itself produce predators. Social norms are quite powerful by themselves. The present system needs to be wholesale re-evaluated for its fairness and effectiveness at producing people that don't reoffend.
At the moment it exists, structurally, to create a labor force that can be forced to work for free, effectively continuing the practice of slavery in this country. This systematized role disproportionately affects communities of color, unsurprisingly, in line with the historical victims of the practice.
>What do you do with the 20 year old man who robs someone at gunpoint, or drags a woman into an alley and rapes her?
Well, at the moment we let them out after 90 days if they're on the swim team at Stanford.
https://www.cnn.com/2016/09/02/us/brock-turner-release-jail/...