Rato brings up a great point. There is NO perfect solution.
Todays cars are SO much more efficient and environmentally friendly than those of 15 or 20 years ago it's unreal. It was not that long ago that carburetors and extra weight made for MUCH dirtier and more fuel hungry cars. 20 MPG was a really economical car unless it was very small. NOW our moderate sized SUV's, such as my wifes 4Runner get 20MPG. Nowdays 20MPG is almost considered a fuel hog. The emmissions from this car are a small percentage of those emmitted from a similar vehicle of 20 years ago.
We have taken great strides in fuel efficiency and emmissions control. But, there are laws of physics that prevent drastic improvements without moving to newer technology. That technology is coming, just be patient.
In the meantime, let's not consider someone the AntiChrist because they choose to spend the extra money to own and operate a larger vehicle. This is America where we all have the right to do what we please as long as it is legal.
Have a great day,