My girlfriend/SO's grandfather died last night, running on a treadmill when his heart gave out.
He wasn't signed up for cryonics, of course. She tried to convince him, and I tried myself a little the one time I met her grandparents.
"This didn't have to happen. Fucking religion."
That's what my girlfriend said.
I asked her if I could share that with you, and she said yes.
Just so that we're clear that all the wonderful emotional benefits of self-delusion come with a price, and the price isn't just to you.
Well - it is my girlfriend who said it. I think the primary damage done by religion to atheists is the propagation of such things as "No one can possibly know" (which even some atheists unthinkingly repeat), a general tradition of avoiding the subject, an idea that you can say anything you want, and the contamination-by-association of any possible trick for living on after you stop by breathing.
The question you want is: in a world where religion had never existed, but people's reasoning abilities were otherwise mostly the same level, how many people would now be signed up for cryonics? This is the damage done by religion alone.
Arguably religion does the most damage by de-legitimizing concerns like immortality and discontinuous world-changing events by surrounding them with a cloud of wishful and otherwise mistaken thinking.