This might sound radical, to the point of nonsensical – but actually its very practical.
Resources like time, HR and money are limited. And where you spend those scarce resources can be a big strategic decision. What if you keep wasting those resources on a few sore apples in the bunch? What if most of your marketing resources are spent serving customers who, no matter what you do, are unappreciative of your business?
If such is the order, its time to leave those customers alone. You are much better off by advising your employees to focus on other customers, who are more appreciative. By focusing on those key customers, you will do much better utilization of your resources.
There are some negative word-of-mouth that you just cant control. You just have to learn to live with it.