I disagree as more people signing up for cryonics makes cryonics more affordable (and thus evens out the unfairness of premature death) and also gives large numbers of people a vested interest in the future. Cryonics on a small scale has unfavorable features that it would lack on a larger scale, so you need to be careful not to conflate the two. Note that as far as PR for existential risk goes, you can't beat cryonics for giving people a legitimate self-interested reason to care.