Right, it also serves to remove that person from society as they are a threat to others. When you kill someone, it stops being about you and your "rehabilitation" and more about other people.
That's not correct, and tells something about your preconception. I was told by someone who had been to prison that those doing time for murder or manslaughter are considered less dangerous, they killed their target and that was that. The ones in there for GBH, those are the ones you have to look out for, they have low impulse control and low intelligence and are basically incorrigible.
From a policy POV, the comment is entirely serious and rational, appropriate.