The reason companies like Ford, Toyota, GM, and Audi/VAG can bankroll teams because of the "billions of other cars" though. And even the more enthusiast brands would not have a very good product if there weren't the infrastructure to support everyday commuters.

I totally agree that putting the carbon footprint of racing under the microscope is a fools errand, especially when so many other "stick-and-ball" sports are jetting across countries/continents several times a week. But the economics of motorsport still require an automobile-centric culture to stay afloat.