Rehabilitation doesn't have very much success. It doesn't have any deterrent effect. Your ideas may make you feel good, but without effective deterrence, crime would soar. "Punishing the remorseless" does have an effect if you do it right.
The fuck? Rehabilitation starts BEFORE the "monster" becomes a social pariah. Not once a person's in the system, not once they've had a chance to devour the lives and souls of others. I've had a chance to sample this nation's platter of "rehabilitation." I've also met those that were a part of pre-Reagan "rehabilitation" (aka lobotomized patients, electro-shocked patients, and experimental drug patients.) Met each and every one in libraries, or bus stations, travelling the underbelly of the nation, fucked up because prisons and bombs are more important than understanding that human beings are NOT a static creature, we're an evolving species, and we shouldn't have our brains scrambled just because we're different.
And, again, I aver. You start talking about lining up monsters in droves, to shoot them as "examples" and guess what you're going to get? Ultraviolence. A bit of the old in-n-out, and a whole lotta' blood. "Monsters" are just that. You trip a group's collective self defense mechanism and it'll get ugly. Of course, it's a mostly moot argument. Those in power, setting pen to paper know that THEY have the same "mental defect" allowing them to ascend to power and fame as the monster at the other end, turning into a mindless killing machine. No Governor wants to sign his own death warrant.
A lot of people don't realize a few things. We tried the "set an example." That DOES NOT WORK. If you cut a thieve's hand off, you create a bandit, and a leader of other bandits. The risk:reward factor is balanced, when GBH may be the punishment for either crime. This is why we don't execute rapists and child molesters, or kidnappers (with rare federal exceptions, and Louisiana.) You see, if you give a monster the choice of letting the victim go, with threats, and knowing the WORST is life w/o, you still know you aren't going to be killed by the state. When you remove the disincentive to leave the victim alive, you get more dead victims.