4 is the biggie, all the others are pretty small in comparison. Union of concerned scientists sez the kind of car you drive has more impact on the environment the everything else you do combined, which sounds about right to me.
I drive a small compact car, often times car pooling to the beach. By comparison, the windsurfers often ride up in monster rigs, generally one per truck. Since my 4 kite quiver can cover such a wide range I generally ride the closest beach, instead of hunting super strong winds or flat water.
Seems like we can all agree, windsurfing is way worse for the planet then kitesurfing. Let's not even get into wakeboarding, and I know several ex-wakeboarders that have sold their boats for kites.
The surfers I know also seem to do lots more driving, since the closest beach doesn't have that perfect curling wave. The launch ramps there are plenty good for me.
Kiteboarding isn't a flawless activity, but it's probably one of the least enviro-harmfull ways to get your kicks. Maybe log onto an off-roading forum and lecture those guys.