What's the worst example of "not reading the room properly" have you seen?

A guy told me the end of the line was behind him. It was the third time -. I'm just waiting..I said "Oh, you're right, everyone must be before me!". He said"Shut up- it's alright to cut in front of you, you're okay.". I said, stupidly,"No, it's not okay,the line is just as long as in the Soviet Union in 1989, but we're paying a whole lot and working away our lives, here..." Guns came out. "Politics? No politics, lady.". ... I was still thinking of chattering some more... Two more guns came out.....
Great Fred Meyer. Open minded America.