He was wearing a cycling shirt in his car??? Maybe he was on his way to a race?

The problem with his analysis is that it is usually phrased "as close to the right as practicable", not "possible". That gives you more room for interperation based on the situation. I interpret it to mean "as close as is safe", which could well mean your riding position. I don't know your road, but from what you've described, I'd say you were within your rights. But check your state bicycle statutes so that you know exactly what it says. Try Googling "Oklahoma bicycle statutes" or related.

Maybe he honestly thinks that as close to the right as possible is correct, and he tries to do it (not realizing he doesn't have to), then he sees you and gets all self-righteous that he works so hard to do it "right" (he thinks) even though it's a hassle with all those cars passing him too close and everything (maybe the reason he's driving instead of biking on that road), and here's this other guy giving cycling a bad name by doing it "wrong" (he thinks).