The use of "back yard" refers to the local area, not the literal extent of one's property. This usage is not unique to NIMBY and it's derivatives. YIMBY sentiment also clearly extends beyond developers themselves and simple libertine principles. Many people want development to occur around them, in their back-yard so to speak, because they prefer it occurs. The semantic change you're arguing for erases this concept just to sidestep the notion of local community. It's a needlessly aggravating approach when the simple answer is just that both NIMBY and YIMBY advocates can support their cause beyond their own area because they believe their cohort is right and deserves it.

They are telling communities that they have no part of how to manage themselves.

Rancho Palos Verdes should not be required to comply with the request of some random activist who probably has never even stepped foot in the town.

I mean, also not in my back yard if the people who don't own the land vote for a bunch of micro managerial laws that make it illegal to do things without jumping through hoops that are so expensive as to be a non-starter.

Nobody is gonna go through the "everything else" approval process that strip clubs and heavy industry have to go through just to expand their business parking or do $10k of environmental impact assessment to drop off a $1k garden shed. (literal examples from my town).

These evil people can't make things illegal outright so they make the process so expensive almost nobody can do it and it takes decades for someone to come along with a lucrative enough development that's worth expensively challenging it inn court over.

> More housing in region X will result in lower housing prices in region Y.

Or higher prices in Y, because X will be both more crowded and with on average poorer people than before the supply increase, and people who prefer a less crowded area and less poor people (either directly because they are poor, or because of other demographic traits that correlate with wealth in the broader society, like race in the USA) around them will have an even higher relative preference for living in Y than before.

> The interests of people from region Y are valid.

They exist, validity is...at best, not a case you have made. Existence of a material interest does not imply validitym

I can say their interests don't meet a threshold of significance.

As an extreme example, I can say that hurricane victims have an interest in butterfly wing flaps across the world because there is some indirect causation.

Housing expansion advocates consistently describe the simplest of supply-demand mechanisms, whereas housing demand is heavily driven by local and national economic conditions as well. Gary IN doesn't have a housing shortage.

That's a very theoretical argument, and there's nothing stopping people in region Y from building all the housing they could possibly need in region Y. If it's such a great idea, region Y will thrive and reap the rewards of this policy.

And my point is that there are limits on the impact region X has on region Y based on their proximity. Should someone in downtown LA be able to compel someone in Palo Alto to upzone based on this "impact"? What about someone in Kansas or Florida?