Imprisoning people who have committed crimes is not cruel. It's literally the job of every justice system to do that.
If there was some sort of abuse then sure, but there hasn't been to my knowledge.
This makes it usual or common, but it doesn't make it not cruel.
> Imprisoning people who have committed crimes is not cruel.
Imprisoning someone is absolutely cruel. It may be common and accepted (and it certainly is in our current criminal justice system). It may even be just and proper, but it is still cruel.
That's not what is being called into question. It's imprisoning someone for the express purpose of coercing testimony that smells here.