Criminals should labour to repay the damage they have caused to society, its citizens, and their property. Morality is clearly based upon rather subjective metaphysical notions, and is by no means universally accepted. It therefor should not be the basis for any sort of state policy. Retribution is similarly ill-motivated, in that it appeals to the worst instincts in people. These instincts of violence and veangeance, however, are not things which should be catered to or encouraged.
Rehabilitation seems a little bit more enlightened.
The idea of rehabilitation of criminals raises several questions, however, which have yet to be successfully answers. Perhaps merely punishing him is not the best way. Perhaps he needs therapy. Perhaps he needs counseling. Perhaps he needs medication, or perhaps he needs an operation.