If you drive, this has probably happened to you:
A car ahead of me does something irritating, like swerve into my lane, drive 65 in the left lane on a freeway, or block traffic trying to make a left turn when there's a sign that says "NO LEFT TURNS 4-6PM M-F". I drive around and peek through their window to take a look at the driver.
But why do I do that? I might excuse myself with something like, "I want to see the face of my enemy!" but I bet the real reason I do it is to establish or confirm a stereotype for who is or is not a bad driver, based solely on physical characteristics. Moreover, stereotyping based on the car's physical properties might make sense, but stereotyping based on the driver whom you normally can't even see? Well, there's just no real excuse for it. Yet, I do it all the time. Odds are, you do too. It's human nature.
I still feel kinda bad for doing it, though.
And then I drive on.