>Is there some reason I should side with you over them, or just your opinion? If the courts decided that there was an expectation of privacy on public roads, would you agitate to change the law so there wasn't?

Sure! It would make infringing on road safety much more difficult thus reduce your chances of getting run over by people who are speeding, running red lights etc. And if you're driving, I think everyone would enjoy less maniacs on the road.