On first reading, this argument--from the right wing American Thinker--is actually kind of clever:
In fact, if the left truly cares about preserving the environment, reducing carbon emissions, saving the planet, and all that glop, then it should wholeheartedly embrace conservative social values. Consider stable and traditional marriage. According to the Census Bureau, 96.6 million Americans over age 18 are unmarried and 31.7 million Americans (27% of the all households) live alone. This trend towards Americans living alone or out of wedlock is rapidly accelerating -- and it is destroying the environment. A stable married couple lives in a single home, has only one set of utilities, illuminates the home with a single lighting system, and economizes on overhead in many other ways. Adult Americans who live alone or in unstable relationships dramatically increase the need for dwelling space, electrical power, heating and cooling systems, streets and city maintenance systems, and also cars on those city streets. Moreover, in traditional marriages which reach a level of economic affluence, it is more likely that only one member of the family needs to work, reducing traffic congestion and all the myriad environmental problems of a large and commuting metropolitan population. If Americans married and stayed married, the impact on all those problems which leftists pretend to worry about would dramatically diminish.
There's more along those lines, too. But two can play at this game. By the same logic, it's time for the American Thinker and social conservatives to embrace gay marriage--due to the vast environmental benefits. I'm sure that concession will be coming shortly.