Many murderers murder openly and don't get any jail time at all. Cause they are elected politicians.
Other than that - the purpose of the penitentiary system is not to punish people, it's to redeem them. At least in theory. You don't have any right to punish other people (well, an eye for an eye may do, if there's no other way, but that's the worst that's acceptable), especially with such intentional destruction as a life sentence.
There are conversations where the actuality matters, and there are conversations where the criteria matter, and there are also conversations where the dynamic matters. You mixed up this one.
I mean, everybody talking about someone else's rosy worldview or otherwise playing a cynic is usually clueless.
You know, one can inflict trauma that won't be forgotten in 10+ years without any rape. Which wouldn't be a cause for even a fine, or a day behind bars, or lower social prestige of the person doing it.
While with rape - I'm all in support of killing attackers in self-defense, it's justified.
But if the crime is already done, and if you have them behind bars, and the facts are established, then every hour and every day their personality changes, and becomes further and further from the one that committed that crime.
And the purpose of the system in theory is not to punish or destroy. It's to redeem. You are nobody to attempt anything else.