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.
Not by the standards of the majority of the human race.
But yes, if you're discussing something, it's generally worthwhile to investigate it somewhat.
The failure of thought in that quote seems to me to be that she came up with an idea of how it could work, and assumed that was what other people believed. Much like people who hear about evolution and assume it says monkeys turn into men.
Due to finding this idea ridiculous, she didn't bother to find out more, but instead spreads the ludicrous-sounding version she came up with.
Information gaps that harm people are not to be less hated for being commonplace. However it does imply is that the person isn't as likely to be the problem. And I can see how the reaction of condescension towards the person might be less likely to result in productive reforms than another reaction.
But if not condescension, then what? How can this gaping hole in the knowledge of most of humankind be filled? Heck, how do we get people to even realize it exists? What is the more appropriate emotion to level at a world that, by and large, just doesn't get 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.