You were chumped by that bitch.
I remember one time, it was right before xmas, I was at the local grocery store trying to check out.
I got in the express line, which had a sign that said it was for no more than "X" number of items.
The guy in front of me had a full cart, and started to unload it.
I barked at him that it was an express only line, he was in the wrong line, and told him that he needed to get in the right line.
He looked at me as in "How dare you!" then started mouthing off.
To make a long story short I stood my ground, yelled back just as forcefully then glared: he removed his items and went to the right line, cowed.
You can't take shit from people, they'll run over you if you don't stand up to them.