Also for violant criminals. Remember that also a major purpose of a prison is to reenable the people to insert themselfs in our community when they are through their judgment. Normally it is already difficult enough. If someone say got 5 years for [insert some crime here] and all you do is to torture him 5 years, afterward not help himself, well then he will have not choice but to fall into a crimenal life again.
For example you have to let them watch the news, read a newspaper, to keep themselfs informed, you have to keep the somehow busy on an intelectual level, prepare them on the job that they have to do afterward. If the sociaty makes it impossible of prisioners to job afterward a prison-verdict they will have no choice but to continue their criminal career.
If you want to treat them all in prisons like **** you can also kill everybody for everything. Meaning not just murder but any crime that is punished by imprisonment.
Where do you get that we kill everyone for everything? You do not know anything about America but what you read.