Things like this are 90% self-confidence and 10% innate weirdness. Talk about it like it's obvious, normal, and you're part of a community of smart people out there, and they'll pick up on the cues.

I know saying that won't help a lot of people, but it's what I do. When I introduce cryonics to someone, I don't sound nervous and timid and censure-expecting, I take off my necklace and say "This is my contract of immortality with the cult of the severed head."