A reader sent me this NIMBY flier from my old college haunts of Cambridge, Mass. and it's a great example of the rhetoric of reaction in action in a community that probably thinks of itself as very progressive and forward-looking. Obviously the core underlying point here—that if more residents and more employment come to Cambridge things will be more crowded—is true by definition.
But one interesting fact about this is that I imagine many Cambridge residents consider themselves advocates for affordable housing. As it happens, right now the median value of owner-occupied housing in Cambridge is about $560,000 compared to $352,000 in the state of Massachusetts and just $188,000 nationwide. So it's clear that status quo Cambridge is actually an extremely desirable place to live. If somewhat increasing the city's population really did somewhat reduce the desirability of living there, it would still be a much-more-desirable-than-average place with much-more-expensive-than-average homes. Consequently, the average standard of living in the United States and in the Commonwealth of Massachusetts would go way up.
Now, again, maybe Cambridge residents just don't care about the welfare of their fellow citizen. But if you put it to them squarely, I bet they'd say they do. These are voters who favor, quite sincerely, progressive taxation, and a robust social safety net. They just don't think of these local policy issues in the same terms, as questions that have broad implications for human welfare and aren't just of parochial interest.
Meanwhile, it's far from obvious that this greater density really will decrease quality of life. Consider the issue of buses. The more customers a given bus line attracts, the more financially viable it becomes to increase frequency on that bus line. But greater bus frequency benefits everyone who rides the line. In other words, a denser town offers a higher-quality bus experience, not a lower-quality one. It's drastically cheaper on a per capita basis to provide certain kinds of public services—police, fire, street cleaning—in a denser city. Your libraries can keep longer hours. Your public school system can offer families more choices or less travel time.