Eh, it's possible to take this kind of self-interest too far. Like by the same token, you could say, "well, it's only natural for non-poor people to shoot down programs that will help the poor, because it's not in their interest".
Like, expecting people to give up a little for the benefit of wider society is not unreasonable. We're not talking about forcibly seizing people's homes here, just about allowing their neighbors to sell to developers who will build more housing. That's not exactly a huge sacrifice.
I think people are afraid of change, not because they know it is not in their best interest, but mostly because they aren't sure, so the status quo seems to be the safer option. It's why humans are averse to change in a lot of scenarios, we sometimes have a little bit of trouble with the long term perspectives.
Sure, and even people that oppose change on one axis (like density) often support other changes in their city.
People, of course, disagree on what changes are desired and which are disliked, but that's the nature of subjective preferences.
Well, except that cities, even if viewed as "organisms", aren't people, they serve people, and its quite natural for people to want them kept in the state that they feel best serves their interests.