Dealing with a demanding customer can be a nightmare—ask anyone in customer service. It's not as straightforward as you might think either—the more you bend and break for them, giving in to their demands, the more they will ask for in return. It's like a lion attacking a herd of wildebeest; the hunter can sense the weakness, and showing any will make you a greater target. Plus, if you actually manage to close a sale with these people, there is an infinitely greater chance that they will become…