You've just dismissed an actual useful datum concerning an objection. How often do you hear someone state their squick so clearly?
Honestly, people who don't know about vitrification or organ regrowing are ignorant. The made up detail about swapping "just any old body" does not impress me much.
Perhaps they are trying to say something other than what it sounds like they are saying, such as that a regrown body (even from their own DNA) wouldn't match the brain closely enough for that to work. If that is the case they should make that claim, and defend it with facts -- instead of wasting people's time with ridiculous mental images of grabbing a random corpse and stitching the new head on it.
The BBC News recently ran an interesting piece on living forever. They discuss some of the standard arguments against cryonics and transhumanism; overall, the article is pretty critical of both. I suspect most LessWrong readers won't find it convincing, but it's still worth a quick read.