The real problem is that a lot of suburbs are just depressing: tributes to the willingness of Americans to accept mediocrity (mediocre schools, mediocre restaurants, mediocre houses, mediocre cultural amenities) and to pay an increasingly high price for it (traffic, home prices, property taxes, no better connection to one's neighborhors than in an anonymous urban high rise, higher and higher energy bills).
Conservatives can be just as depressed by this as anyone else, perhaps even more so than liberals. However, an important difference between liberals and conservatives is that we're willing to let people make their own choices and have confidence that the market will ultimately sort it all out.
Yes, suburbia does not take up much land, but it gobbles tax dollars, wastes infrastructure, creates stress, becomes part of a combined domestic environmental cocoon wrapped in congestion, pollution, and due to faulty planning, induces social and intellectual isolationism, obesity, etc.
We need more mixed use/high density to make America work and live better, longer and healthier. And not waste resources: paving, sewers, water lines, electrical lines, sidewalks, rescue and services, gasoline for irresponsibly long commutes, etc.
We take up a very small fraction of the available land, yes; but we consume the majority of our resources in these areas.
Speaking of which: if the recent scare price of over $200/barrel as projected by recent CNN story comes to pass, our suburban model will become extinct.