I'm not quite sure what you're getting at. People in urban areas have lower carbon footprints than people in car-dependent suburban and rural areas. No one has a zero or negative carbon footprint unless they do something to actively offset their emissions. I don't think most city dwellers are self-satisfied jerks. A few are, but then does it really have anything to do with the city?

Ultimately, poking people in the eye about their consumption habits is counter-productive. Cities are efficient, but not efficient enough to prevent global warming. This problem is only going to be solved through technical innovation and government regulation.