Professors with PHD's

Out of my few years in college, my professors never cared whether I called them Mr./Professor/Dr. _______.  It was never an issue.  Recently, I ran into a professor I vaguely knew but never had before and asked him for directions to a classroom.  I addressed him as Mr. ____, unknowingly that I was about to get my butt chewed out.  He looked at me with a very I'm-better-than-you gauze and said, "You will address me as Doctor, and nothing less, is that clear?".  Taken aback, I stood there for a few seconds and just stared at him; do you really have that much of a superiority complex that you need students to address you as "Lord Pretentious Dr. ____"? It's an informal setting, I was simply asking for directions - I wonder what he says to students who may not even KNOW his name to begin with?  "Address me as Yoda, inferior one, for I know your destiny in life". Mmm... perhaps not my best Yoda impression.

I walked away from him without a response, but I started thinking about it more next class (Eco 101, it's not a very entertaining subject for me...) when you think of Doctors, do you think of them as someone with a PHD in whatever subject, or as someone in the medical field with an MD?  I think of them as someone who has medical background, with an MD, not an English major with a PHD who is self-centered and insecure without his title in front of his name.