"Thank you for seriously engaging with my beliefs" is something that makes sense much more broadly.
I do think that there is something low-status in the phrasing. "Thank you for taking my beliefs seriously enough to criticize" I would call creepy. I suspect that there is a better way to phrase this. "Thank you for the debate" is a perfectly ordinary statement, but probably not adequate for this situation.
Luke Parrish points me to what is clearly by far the most serious critique of cryonics ever written: a 57-page treatment by Evelina Martinenaite and Juliette Tavenier, presented as a 3rd semester project at Roskilde University in Denmark supervised by Ole Andersen.
Full paper