I think this is the root of it. You prefer higher density -- and that's great. I'm sure not everyone agrees, but I don't see any reason to take that away. In fact, I think it should be encouraged for those that like it.
The issue, IMHO, is that some folks don't like that and prefer lower density. And a lot of these changes focus on taking that away from them (i.e. changing their current neighborhood).
Also, just a comment on: "It has to create more car dependence and social isolation"
I don't think that's true. I live in a pretty traditional SFH neighborhood. Within a 12 minute bike ride, I have:
* Four grocery stores (Major chains)
* 2 gyms
* Dozens of restaurants
* Several large parks
* 2 home improvement stores
* Several large employers
* Several (non-Starbucks) coffee shops
And lots more. It's certainly possible, with bikes, to have SFH neighborhoods where cars aren't required.