You could have made him feel like a REAL TOOL by getting out and helping him push his bike off to the side of the road and being real friendly to him. He would have felt bad about giving you the "bird" for a long time.
As another biker I would have gotten out an helped him. Also would've let him know full well I ride also and that's the kinda crap that seperates a biker from an idiot rider, not to mention making every cage care less and less about us on the road. Then I would have told him he'll understand what I'm saying oneday when he moves up to a real motorcycle...after helping and he thanked me, as I drove away I'd beep and give'em the bird.