Punishment is only really getting revenge for the vitcim, without this it's just a lazy man's rehabilitation. Whether someone should have one or the other is entirely subjective. Is revenge needed? A bit, in my opinion.
There's been a lot of news recently about pedophilia incidents, some people believe no amount of rehab will help and full punishment should be administrated. In that perticular case it was arguable whether or not the victim was a victim, another subjective matter.. and so to me it should be purely about the rehab. Doing something that leaves someone physically or mentally hurt desveres a slight weight of punishment, but that's just me. You could claim that every crime has a victim, and so the punishment is always needed.