All human beings have the capability to think. Why should a human being, perfectly able to think, be imprisoned in their minds? By allowing and teaching free thought for prisoners through philosophy, the prison system will serve its purpose as a rehabilitation center and lower chances of having re offenders.
Prison should be aimed towards helping those troubled people recover and learn from their mistakes. If the prisoners wish to learn something, anything, they should be allowed to gain access to that knowledge. It is important to teach everyone because knowledge is a wonderful thing. It is also important to teach people when to and not to use that knowledge.
Philosophy should be taught in prisons because prison should be a place to rehabilitate those who have made mistakes. Unless someone has been given a life sentence, they have the possibility of being released, and philosophy may help open them up to doing good when they get out of prison, or at least thinking of the world in a different way, which everyone should have the capability of doing, prisoner or not.
If philosophy is taught in prisons all that is happening is that prisoners are learning more about life and the world around us. It is a great thing and the more time that can be spent learning as opposed to getting into trouble is beneficial to prisons. Philosophy is a wonderful subject that many would enjoy if given the opportunity to do so.
All philosophy is, is the search of truth and reality. I imagine the study of this would go real far in helping people understand the factors of why they are in jail and how to stay out. However, for the many of the people that are there for crimes with no victims, they may have a better understanding on how it is all big scam that placed them there. This may not be in the interest of any prison.
I think that the teaching of philosophy in general is a huge waste of time. To teach the concept in prisons is an even bigger waste of time and money. The people behind bars aren't exactly aspiring Aristotles, and to think that they could be is a huge mistake to make.