I thought that most people considered p(singularity in the next 40 to 50 years) to be vastly higher than p(cryonics works and nothing goes wrong)
I'm not sure that's a universal feeling. I would certainly would put it the other way around.
But there's another issue that is going on here. Many human moral systems allow one to kill others to save a life. Under many moral frameworks if a person of age x is trying to kill someone of age y > x, it is still ok to kill x. Many different justifications for this are given, but it seems to me that the basis might be best thought of in terms of decision theory as a strong precommitment to stop murderers even if it means killing them. If in such a framework one views a cryonicly preserved individual as morally akin to a living person then this makes sense. Moreover, even if one does agree with the calculation that you suggested, similar lines of emotional pulls (and tribal loyalty to people who engage in or support cryonics) could easily move ones attitude towards indifferent.
I'm not sure that's a universal feeling. I would certainly would put it the other way around.
What are your exact (or, I suppose, approximated) probabilities? Maybe I don't have a good sense of this.
Many human moral systems allow one to kill others to save a life.
Well yes. This brings up a whole host of issues though. The best analogy to the point I'd like to make would be abortion. Similar to fetuses, human moral systems do not view corpsicles as "lives". Which is why those moral systems you mentioned wouldn't approve of murdering someone ...
Check out the latest episode of Castle (Headcase) to see Cryonics covered in mainstream fiction in a not entirely terrible manner. The details are not exactly accurate but probably not more inaccurate than similar fictionalised coverage of most other industries. In fact there is one obvious implementation difference that the company in Castle uses which is how things clearly ought to be:
Amulets of Immortality
It is not uncommon for cryonics enthusiasts to make 'immortality' jokes about their ALCOR necklaces but the equivalent on the show make the obvious practical next step. The patients have heart rate monitors with GPS signalers that signal the cryonics company as soon as the patient flatlines. This is just obviously the way things should be and it is regrettable that the market is not yet broad enough for 'obvious' to have been translated into common practice.
Other things to watch out for: