RV'ers use less energy and resources than living in a house. The RV took less resources to make by a long margin. The life of a typical RV is not as long as a typical house. A house takes more maintenance than an RV. By traveling to wild areas (or near them) we promote the saving of these areas rather than development.
Before the back slapping stops, just remember, the US has 4 percent of the world's population but we consume 25% of the world's petroleum output. I don't know the facts but I'd bet we are also out of balance with other resources like grains or foods, and various minerals.