I have to admit, I'm conflicted over the right answer to this. I do believe that the kind of motorist who honks and yells at you to "get on the sidewalk" is the sort of person who is oblivious to reasoned arguments. However, they also may respond to humiliation. In other words, these are the sort of people who are driven by emotions rather than reason. The problem is this -- it's not easy to humiliate a motorist surrounded by two tons of steel while you are on a bicycle. And in some areas, you may actually inspire them to use physical violence against you.

So the consensus seems to be that the best thing to do is just go on your way and ignore these asshats. I freely admit sometimes this is VERY hard to do.