While you can argue about the stupidity of the ban on certain substances, and how it has caused many people to be locked up for the dumb offense, you cannot deny that prison is a concentration of mainly degenerates in society. Those that are more mild in nature are quickly hardened by the environment. Though this is talking about the maximum security prisons.
Even in a group that has no regard to the law, there are rules. There are certain types of people that these people hate. The first are people that commit crimes where the victim is a child. The next most common one are snitches. Chances are, they were locked up because of witnesses.