"....because you are stupid!"

So I had another run-in with a retarded customer. My day is usually filled with them but there are just certain attitudes that really annoy me. This customer wanted to return an item without a receipt. I explained to the customer that our store policy states that if there is no receipt present all I can offer is a store merchandise credit card, which is only valid for purchase. This woman started speaking at the top of her voice because she was not pleased with her option because she is a "valued customer." In my mind I'm thinking, "If she shops here all the time then she does not lose if she gets a merchandise credit." Any who........ I told her, "Miss I would be happy to continue to assist you but I must ask you to lower your voice" She said "Don't you tell me to lower my voice little girl." and continued with her dramatic display. I looked at her laughed, walked away and called my manager to finish with her. In the end she still got a merchandise credit card. About 15 minutes later the same customer comes up to me and says, "this is why you work at Urban Outfitters because you are stupid!" She did piss me off but my fist reaction was to just burst in laughter. She really thought that a comment like that would have made me react with some kind of violence but I gave her what she didn't expect. The look of confusion on her face while I was laughing made that entire moment very priceless.