I'm always a bit wary of western "environmentalists". Nearly all of them have a carbon footprint and way of life that is not at all unsustainable on a global scale. Instead of asking ourselves if such and such car or product is green enough, we should focus on trying to remove these sources of pollution and find better alternatives.
Summary: Everyone wins! The Tesla can be as green as you want it to be depending on how you calculate the green-ness. In other news, high performance luxury sedans have somewhat higher mass and are easy to drive at/with inefficient velocity and acceleration.