I actually go out of my way to wave at scooter riders. It's fun to watch them try and keep control with only one hand on the grips...
Honestly, I'll wave at most anyone one two wheels - including scooter peeps. Some of those scoots are pretty cool, and some cities even have clubs with organized club rides. NOT waving would make me feel like an 'elitist' or someone who rides a Harley and thinks less of anyone riding another make of bike.
