I was kind of horrified how bad the arguments against cryonics are[0]. As far as I can tell noone has ever gone to the trouble to seriously and in good faith argue against it, they just apply the absurdity heuristic and say its advocates are freaks/frauds etc. (And yet I have not made my contract of immortality with the cult of the severed head.)
[0]lesswrong.com/lw/1r0/a_survey_of_anticryonics_writing/