That stuff never bothers me, I usually point to the sign and say something like "earned it" or "its a choice"
Last Friday when I went to the AVIS line at YVR there was one agent working and he was finishing with a preferred client and there was four lined up at the other regular line, I saw them, I walked up to the preferred, I glanced over at the four with a smile, showed my Drivers licenced , signed the card, collected the keys and in 20 seconds I was walking away.
As I passed the four they looked at me and I simply said, " earned it" and walked on.
Most AC staff simply do not want confrontation!