When people honk in situations like that they're not saying "Hey! Move over, will you!" - they're saying "Hey!! You shouldn't be on the road, MORON!"

And there really isn't any response to that that won't bring you down to their level.

I'd probably pedal my *ss off right in front of him until I could wave him by with all the regal manners I could muster. Then sulk all the way home.