It's so strange that in different parts of the country people treat you differently depending on what you're driving. Around here, BMW's are as common as Hondas and I can honestly say that I've never received any special treatment because of the car I'm driving. In fact, I've never had any random person even comment on my car. And I keep it clean!
On the other hand, this is Boston, so we don't pick favorites on who we're jerks to on the road. We give everyone equal opportunity to be cut off, honked at, yelled at, and generally abused!