I think we underestimate our own evil. Tomorrow any of us might answer our mobile while driving and crash into a dozen schoolchildren. We could then be a prisoner, too.
What about truly evil prisoners? First, beware to not give personal information if you should not. Second, really evil people are still people - there are hundreds of good arguments to show them some love and mercy. Are love and mercy now dirty words?
I am actually sad that Prison Voices says that it discriminates against various prisoner categories. I hope that even the very worst prisoner gets some pen pals, and, by some miracle, is healed at least somewhat.
I may not be a Christian, but I do believe in a lot the ideals of Jesus.