Try commuting on a motorcycle every day. I used to have a thing where I would tell the wife when I got home "well no one tried to kill me today"
As many inattentive and stupid people as there are on the road, I am still looking forward to getting my motorcycle back together so that I can get back out on two wheels.
I definitely agree with those that suggest restraint, there is just no way to know how someone will react, even to something as minor as a hand gesture.