There's a much better, simpler reason to reject cryonics: it isn't proven. There might be some good signs and indications, but it's still rather murky in there. That being said, it's rather clear from prior discussion that most people in this forum believe that it will work. I find it slightly absurd, to be honest. You can talk a lot about uncertainties and supporting evidence and burden of proof and so on, but the simple fact remains the same. There is no proof cryonics will work, either right now, 20, or 50 years in the future. I hate to sound so cynical, I don't mean to rain on anyone's parade, but I'm just stating the facts.

Bear in mind they don't just have to prove it will work. They also need to show you can be uploaded, reverse-aged, or whatever else that comes next. (Now awaiting hoards of flabbergasted replies and accusations.)