I get where you're coming from here- I also don't see justice as an inherent good. If somebody kills somebody else, the death penalty will only increase the number of victims by one. It does nothing to undo the crime. Karma isn't real.
But you have to think about second order effects. The knowledge that you may be punished afterwards serves as a disincentive for doing the wrong thing now. It may be preferable to convince everyone that they would be punished without actually doing the punishment, but it's not possible. Apart from the death penalty, punishments also can directly teach an individual not to commit the crime again.
Right, I just responded to that claim. Do you have any thoughts on the disincentivizing effects of punishment?
Or, if not, we can be more specific. Imprisonment means that an individual is separated from society, making it much harder for them to commit crimes. Most crime is done by young men, and time spent in prison contributes to age. Issuing a 10-year sentence means directly reducing the number of crimes that occur. Is that not beneficial to society?
Or if a CFO embezzles $10M, should society be indifferent to whether taxpayers make the company whole or the CFO does it?