I finally got the chance to have a civil conversation with a driver who honked at me as he passed me.  It went something like this:
    Me: Is there any particular reason you honked at me?
    Him: Yeah I honked at you.  Not really what I said, but as you'll see later, his listening comprehension skills are the least of his worries.  It's illegal to be in the middle of the lane.
    -It's what? Can you point me to that law?  It's not one I've heard before.  Maybe it's new?
    -Oh yeah, I'll just whip it out.
    -You need to, because you have no idea what you're talking about.  Why did you have to honk anyway? We're in different lanes!  Then the civility is lost...
    -F*ck you!  The ingenuity of these comebacks never ceases to amaze me.

I was also once told (a year or two ago) that I have to stay within 10 inches of the curb by a guy that decided it was worth risking my lift to get in front of me at the last minute at a red light before slamming his brakes on.  These two incidents lead me to believe that perhaps not all honkers are angry, but simply un/misinformed.

However, I still think that if you're going to get into a shouting match over road laws, it would behoove you to actually know said laws.  (In case you weren't aware, neither of these gentlemen were quoting actual law, even though I'm sure they would have sworn on the holy Bible that they were.)