"Sometimes you need to fire your customer. It's not easy because it means loss of income, implication of someone's failure (your or theirs), or can even result in making a business enemy.
In fact, the customer is not "always right," particularly when a basic incongruity crops up in corporate culture between your client and your company. That is the time to gently disengage."
Trecho retirado de "Firing the Entrepreneurial Client"