[Epistemic status: very unsure. I sympathize with many YIMBY ideas and might support them on net; this post is me exaggerating the NIMBY parts of my brain to a degree I'm not sure I honestly support. This focuses on San Francisco to make it easier, but other cities exist too. Thanks to Nintil for some of the bright-line argument in part four. Conflict of interest notice: I live in a lower-density part of Oakland]
Everyone I know is a YIMBY – ie "Yes In My Back Yard" – ie somebody who wants cities (usually San Francisco dominates the discussion) to build more and denser housing. This is a reasonable position, and is held by apparently-reasonable people – centrists, rationalists, economists, self-proclaimed neoliberals. Since everyone involved holds reason and civility as an important value, I would expect the discourse around housing to be unusually reasonable and civil.
I have a weird habit of encountering the best parts of some movements and the worst parts of other movements, in a way that doesn't match other people's experiences. And certainly I know many YIMBYs who are amazing people who I love. But as for the movement as a whole, I feel like apparently-reasonable people have dropped the ball on this one. Sorry for having to say this, but YIMBYism is one of the most tribal, most emotional, most closed-minded movements I have ever seen this side of a college campus. So much so that even though I agree with much of what it says, I cannot resist writing a 5,000 word steelman of their enemies just to piss them off.
So here are some YIMBY claims and why I cannot be entirely on board with them.