You're right, it is that there is denser zoning in close proximity that makes us want to live where we do, and makes it walkable. Which contradicts the idea that I'm making a NIMBY argument. I don't want to live in an all-SFH suburb or in a high density zone that's all rentals. I also don't want to live in the only SFH surrounded by condos. I think your point is that the SFHs don't contribute anything to the mixture, and are somehow parasitic on the higher density zones. I think that's not true. Both sides of the mix are important. It gives the neighborhood a character that doesn't exist in most American cities, which is: People of different backgrounds sit together outside cafes and talk. On any given day we hang out with other homeowners, their kids, young professionals, and also people who work in the service industry who live in the neighborhood and go to the same places they work on their days off. We go to concerts with them, they come over when we BBQ and hang out at our house.

My argument is that this arrangement is much better for society as a whole, and for individuals across the socioeconomic spectrum, than a division between all-SFH suburbia and all high-density inner city. Especially now that most people don't commute to an office, and most of the commuting is done by wage workers who have to commute out to the suburbs to work in a strip mall. The homeowners close to downtown provide an economic base for higher-end local businesses that renters would not be able to support. The people who work in those businesses earn enough to rent in the neighborhood where they work. With all high-density, families are essentially exiled to the burbs, there is little to no socializing between economic classes, and everyone has to commute.

Sure, re-zoning doesn't affect individual homeowners immediately, but the endpoint or goal of it is to ultimately get rid of SFHs in inner areas, not to leave a healthy mixture standing. That's what I see as the problem. And I think it's a politically motivated goal based on the idea that no one should really own a SFH (or if they do, as one poster put it, they can move somewhere far away from the city).

In some ways it's similar to the tourism or gentrification problem - the very things that make a place desirable lead to the destruction of those things. Some people view the world through a purely economic lens and treat individual people as abstracted production/consumption units. And unfortunately there's no real way to put a dollar value on "all the neighbors know each other and help each other out". And even if you could - you can't just BUY your way into that, no matter how much money you have! The only way to unlock that value is to live there and engage with the community. Obviously there will be turnover but what some people don't seem to grasp is that there is a tipping point, where enough newcomers overwhelm the "old timers" and destroy the culture of a place. And think about the game theory of it from the point of view of a resident - why invest time and resources in a community if you're just going to leave in a year or two? Or if the beneficiaries are future random people who are not going to give a shit about the community?

"you can't just buy your way into that" is a great insight.

I don't understand what you're trying to say here at all. If you're trying to argue against some sort of development or planning change that doesn't change anything about your own property due for reasons that are purely about how it would affect you personally, that seems like NIMBY to me. The fact that you happen to not be arguing for universal SFH doesn't somehow make it not NIMBY.

Independent of that, I don't really find the rest of what you're saying compelling. You're arguing against a change to eliminate something with concrete, known problems on the basis of wanting to preserve "character". I still maintain that this is indistinguishable from any NIMBY argument.