None of the things you've listed—except possibly the ones trying to self-install a septic system when they already have municipal sewer access—sound like "bad behavior." (And, again, that has nothing to do with zoning.)
What it sounds like is the stereotypical upper-middle-class white suburban boogeyman of "Those People" that you don't want around, because they bring down property values, with a healthy helping of implied racism and explicit classism.
Furthermore, there's no reason why zoning laws couldn't be selectively adjusted and relaxed—for instance, to ensure no heavy industry goes in right in the middle of a residential area, where it's more likely to be disruptive to sleep and potentially polluting.
Acting like relaxing zoning laws to allow for corner stores and similar things will bring us to a Mad Max-style wasteland is exactly the kind of rampant NIMBYism that got us into this mess in the first place.
"What it sounds like is the stereotypical upper-middle-class white suburban boogeyman of "Those People" that you don't want around, because they bring down property values, with a healthy helping of implied racism and explicit classism."
I don't know what it "sounds like" and I cannot speak to your stereotypes.
I no longer have any interaction with residential property, zoning, development, or any of these housing politics. I am not affected by "property values".
I look at these issues as an interested, outside observer and I have tremendous enthusiasm for urban spaces, walkable cities, mixed use environs, etc.
But at the same time I appreciate well regulated[1] single family neighborhoods/developments and while I don't live anywhere like that I appreciate the reasons that someone might have for preferring that.
I hope that it is useful and interesting to you to learn that there are a variety of practical and aesthetic reasons for (not agreeing with you) that come from ideas and experience that (aren't the stereotypes you have in mind).
[1] This is the correct term. Arguing for abolishment of residential zoning is arguing for deregulation.
Everyone says that until their neighbor’s hobby includes heavy machinery at 6am. Then they say “well no that’s this other non-zoning, non-HOA type of law we really do need”.
But really, people want to do what they want, and other folks don’t get to. That’s the whole of it.
That is not limited to “poor people” (your words).