Interesting question...
Assuming the interview is for a retail organization, I think I'd say, "No, of course the customer is not always right. And there are some customers with truly outrageous demands that you're better off not having as customers.
"But keeping an existing customer is much easier and cheaper than attracting a new customer. If a customer has a special request and you can reasonably find a way to accommodate it, do it. Treat every customer as if she's special."