Most of which I agree with, but that I think Jaeger attributes to the wrong people -- i.e., "Urban activists (such as Jack Layton)". It is true that "urban activists" are sometimes involved in movements that cause trouble for urban developers, but as Jay Jardine points out, NIMBYism is the real problem. Thing is, NIMBYism is found everywhere -- not just among the "affordable housing crowd".
One case in point is the Minto Midtown development that is now being sold at Yonge and Eglinton in Toronto. I wrote about it during the mayoral election campaign. The project was fiercely fought by the local homeowners' associations. (These are $500k-$1M homes in a traditional establishment enclave.) Meanwhile, it was (conservative) John Tory who attacked ("socialist") David Miller for voting for the plan that ultimately allowed these giant towers to proceed. (Miller would have preferred smaller buildings but generally endorses intensification at transit nodes -- i.e., developers building big buildings.) If I remember right, Tory talked about limiting all buildings north of Bloor to seven storeys (or something like that).
Here's another case in point -- a more recent one in Scarborough where Habitat for Humanity wanted to build 90 homes for low-iincome families at exactly no cost to the public purse. Scarborough community council voted it down. The excuse was "green space" but the reason was pure NIMBYism. The culprits were by no means "affordable housing" types -- they were politicians of all stripes banding together to hold onto the support of voting homeowners.
Just the same, it is the property-value-watching homeowners who frequently seek to protect their investments by controlling what happens around them, such as basement apartments. I can't say that I entirely blame them. On the other hand, I don't see what Jack Layton has to do with it. NIMBYism is everybody's fault. Well, not everybody, but it can be found in every category of person. Not just the left or "urban activisits".