Leopold saw the car as an environmental demon. He was born and raised in horse-and-buggy time, so as more roads were built into wilderness to allow for the transport annoying tourists, Leopold started freaking out. He thought that cars only further separated humans from nature, thereby making them more anthropocentric. If a tourist's car hit a deer or squashed a raccoon on the road, well, that was just an inevitable consequence of progress. Basically, Leopold thought that the car was just another extension of human arrogance toward nature.