It's really stupid and pointless to go into road rage with any driver. I'm usually very mellow, but in all my years of riding, I did this myself once. It was last summer, after some fat young bozo in a 60's muscle car cut me off and gave me the horn while doing it. I vowed never to do that again. For one thing, with the low level of civilization we all live in now, it can be dangerous. But really, what's the point. Are we really going to change anything? We're just setting up the bozo to buzz the very next cyclist he comes across.