Beware inferential distance. "Everyone should be immortal" includes a lot of unstated assumptions that the person you say it to may not be aware of. They could easily think you mean "Everyone should basically be as they are now, except live forever", which would mean either malthusian misery or draconian restrictions on reproduction. Unless you have already discussed tranhumanism with them, this is a terrible benchmark.

"Everyone should be immortal" is a claim about values, not facts. There's no such thing as "the right conclusion about death".

I tend to use their reaction when I say "everyone should be immortal". Strangely enough it does seem like you need an abnormal clarity of thought to reliably come to the right conclusion about death.

I see this general idea espoused by rationalists rather often. But despite my months on here, I have yet to change my mind into agreement on this.

Aumann's Agreement Theorem leaves us with three options:

1. The vast majority of LW-ers are irrational (I rather doubt it)
2. I am not as rational as I would like to be (I'm sure of it)
3. We do not have common priors (I do think that most anti-deathists are very privileged in terms of: intelligence, wealth, stability, etc)

not even constitute a "lowest standard"

There are a great many people who don't meet the complete standard - in fact, the great majority of people don't; and it seems worthwhile to be able to differentiate between a reasonably rationalist deist and a Californian cloud cookoo-lander.

Of course, any way to differentiate amongst people who do meet the 'lowest standard' is valuable, as well.