Upvoted for the interesting question, then revoked the upvote for unnecessary mindkill-bait.
...but it's still an interesting question. It actually came to mind recently when someone I know and loathe died, and for a moment I thought "hrm. If cryonics was a widespread Thing, he would be less dead, and that would be bad."
It didn't take long to spot the obvious flaw: I'd trade the survival of people I don't like for the survival of people I do in a heartbeat, so the benefits of cryonics as a whole (in the hypothetical world where it works, which I'm not convinced of) still outweigh the drawbacks of bad people getting preserved. That's just the easy question, though. Working out whether it's OK to say "hey, even if cyronics becomes near-universal, specific individuals should not be preserved" is harder. If you believe permitting someone's death by inaction is morally equivalent to killing them, then the question reduces to the capital-punishment question. If you do not so believe...then I'm not sure.
I'd trade the survival of people I don't like for the survival of people I do in a heartbeat
I'd like to know how to get from that position to something more like:
"I want the secret of the Dark Lord's immortality in order to use it for everyone! " (HPMoR)
This month's media thread includes a short article on some people's idea to have Ayn Rand frozen, which ultimately didn't happen. My first reaction was a shudder. I thought, I definitely wouldn't want Ayn Rand preserved forever. My second thought was, What right do I have to say who can and who can't get frozen?
Whatever your thoughts on Ayn Rand, I think this can spark an interesting conversation: What, if anything, should humankind do about people who are widely seen as harmful for the whole? For example, if the Castro dynasty in Cuba or the Kim dynasty in North Korea decide to freeze themselves to ensure they will continue oppressing their countries forever, should that be prevented? (And yes, my opinion of Ayn Rand is such that these examples came to mind.)