I don't agree with it myself as it is essentially the state condoning and carrying out pre planned murder. So no it doesn't make us any better. But it does leave the difficult question of what to do with people who can never be rehabilitated.

Maybe there should be a prison nation where they can be placed to fend for themselves for the rest of their days in relative freedom, where they cannot harm the rest of society?

Or maybe their punishment should be (if they have done something particularly bad) to serve mankind in some way, like sending them on dangerous missions to space or something?