The problem I have with this whole discussion is that it grants what is a monstrous totalitarian perspective a polite hearing rather than the sort of response it truly deserves. It strikes me to just dignify the proposition "the state should spay women and castrate men" with "wouldn't it be better if we just find a way to reduce the fuel we burn?" is to in effect tolerate the intolerable. A far better response, and dare I say a more ethical one, would be "your policy will indeed reduce the world's population because people like me will put a 10mm hole between the eyes of totalitarian scum like you."I'm partial to .30-.30, myself.
I do wonder what sort of dinner parties Perry de Havilland finds himself at, though.