"He seems to think the ruling will bring about affordable housing to the cities' poor."
The urban renewal crowd has been saying that for 50 years, and I agree with you, it NEVER happens.
In 1960, I watched my mother cry as she caught her first glimpse of what urban renewal had done to the West End of Boston where she grew up. What replaced it? Luxury apartments!
http://www.yale.edu/socdept/slc/urban/urban4.html
You'd think that after what Robert Moses did, the urban renewel/eminent domain crowd would be too ashamed to show themselves in public.
In my city, they are now building "Hope VI", the new version of low rent housing. The people living there before the new buildings started going in, had destroyed 5 other incarnations of public projects.