So some guy/girl that calls himself a rationalist didn't get that people can compare outcomes based on gains that aren't monetary? Maybe introduce your friend to some material regarding utility functions or something.
Furthermore I kind of get why you included Crocker's rules in the post (still seems a bit unnecessary) but I did not really get why this is important:
It's a clean illustration and example of the effect that we need to take into account, i.e. the whole reason rationalists have to do this. Once an idea is formed and a "response" is made, it is much harder to change afterwards than if you had been more careful in setting up the "question" in the first place.
Note: I have no intention of criticizing the person involved. I admire that (s)he made the "right" decision in the end (in my opinion), and I mention it only as an example we could all learn from. I did request permission to use his/her anecdote here. I'll also use the pronoun "he" when really I mean he/she.
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Once Pat says “no,” it’s harder to get to “yes” than if you had never asked.
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Crocker's rules has this very clear clause, and we should keep it well in mind:
Note that Crocker's Rules does not mean you can insult people; it means that other people don't have to worry about whether they are insulting you. Crocker's Rules are a discipline, not a privilege. Furthermore, taking advantage of Crocker's Rules does not imply reciprocity. How could it? Crocker's Rules are something you do for yourself, to maximize information received - not something you grit your teeth over and do as a favor.
Recently, a rationalist heard over social media that an acquaintance - a friend-of-a-friend - had found their lost pet. They said it was better than winning a lottery. The rationalist responded that unless they'd spent thousands of dollars searching, or posted a large reward, then they're saying something they don't really mean. Then, feeling like a party-pooper and a downer, he deleted his comment.
I believe this was absolutely the correct things to do. As Miss Manners says (http://www.washingtonpost.com/wp-dyn/content/article/2007/02/06/AR2007020601518.html), people will associate unpleasant emotions with the source and the cause. They're not going to say, oh, that's correct; I was mistaken about the value of my pet; thank you for correcting my flawed value system.
Instead they'll say, those rationalists are so heartless, attaching dollar signs to everything. They think they know better. They're rude and stuck up. I don't want to have anything to do with them. And then they'll think walk away with a bad impression of us. (Yes, all of us, for we are a minority now, and each of us reflects upon all of us, the same way a Muslim bomber would reflect poorly on public opinion of all Muslims, while a Christian bomber would not.) In the future they'll be less likely to listen to any one of us.
The only appropriate thing to say in this case is "I'm so happy for you." But that doesn't mean we can't promote ourselves ever. Here are some alternatives.
I was told long ago (in regards to LGBT rights) that minds are not changed by logic or reasoning or facts. They are changed over a long period of time by emotions. For us, that means showing what we believe without pressing it on others, while at the same time being the kind of person you want to be like. If we are successful and happy, if we carry ourselves with kindness and dignity, we'll win over hearts.