My first thought is: Wow that's really cool, I like that.
I once lived 1 mile away from my office, and walked to work 90% of the time. The people I worked with, looked at me like I was crazy? Oh is your car broke? Do you need a ride? It was unfathomable to them that anybody choose a 25 minute walk to work vs a 5 minute car ride, despite it being cheaper, healthier, and better for the environment.
My second thought is: Hmmm. I wonder if it's really good for the environment? Is he riding his bike alone, or does he have a posse following him in 3 SUVs?