When an irate customer is complaining, or venting, it's easy to get defensive.
You can never win these arguments, and if you take them personally, it's going to be a million times worse. This is when you start to hear business owners saying, "I don't want an asshole like you for a customer!" They get excited about their Pyrrhic victory. Wow, isn't it great? When you're a small business owner you get to fire your customers. Charming.
The bottom line is that this is not good for business, and it's not even good for your emotional well-being. When you win a victory with a customer by firing them, you still end up feeling riled up and angry, they'll get their money back from the credit card company anyway, and they'll tell a dozen friends. As Patrick McKenzie writes, "You will never win an argument with your customer."
I've said this a million times: To be brilliant at customer service is extremely easy. You need just two things: common sense and empathy. The reason good customer service is so rare is that most people have neither.