"properties purchased for the sole intent of knocking down the existing structures to build apartments/condos/etc"
That seems like a particularly cogent example of the Free Market/Capitalism/Invisible Hand at work, at least to me.
The curious thing, again, it seems to me, is the idea that other people who don't have an ownership interest in the "properties purchased" should have a veto in what the purchaser can do with said properties is presented as the Free Market/Capitalism/Invisible Hand just doing its thing.
If the new zoning regulations prohibited building single family housing, well that would be (again, it seems to me) bad too. Do they?