I believe that arguing with an irate customer is fruitless. I listen to them and try to work out a resolution. There was a particularly angry customer who demanded to see the manager of the company that I was working for. He barged in, banged his fist on my desk and yelled the place down. I asked him calmly if I could assist him and he said no. I requested him to sit down and lower his voice so I can understand his concern properly. He explained his predicament calmly, I took appropriate steps to resolve it and he went back calmly!