I think the intent of the Environmentalist DS blogger is lost to a few posters. Everyone rationalizes their path through life and the impact they have on their surroundings. Rarely does this mesh with other's conclusions. I've considered my own actions in very much the same way as the blogger right or not and in the end I have to live with my decisions. Thing is everyone else has to live with the the result of my decisions as well. I'm fine with all of that.
Carbon foot print as has been mentioned is not fuel consumption alone. Afterall all vehicles and just about everything else in this world we use, including many of the technical fibers the "holier than thou" crowd uses in their pursuit of happiness are all derived from fossil fuels. Paint, cloth for seats, shoes, buttons...thank you oil.
What the blogger may have missed is the reason everyone else is there...to get away from the sounds, smells and effects of modern urban and suburban living. My carbed bike does leave a funk in the air. I don't like that but I do my best to be as polite as can possible to hikers, equestrians, and cyclists. A nod and a wave can go a long way. I can see why some of the outdoorsmen he and we all have met from time to time out and about could give us the stink eye...I have just ruined their idea of getting away. Oh well, you can't please everyone.
I don't get the feeling the blogger is what many of us call an Environmentalist but he is us...at least at some point in time. He also assumed people approach their activities with a conscious thought to their environmental impact. I would guess most don't give it a second thought. Or they do and come to a different version of "low environmental impact".