My own experience is that entrepreneurship is a character flaw. Entrepreneurship is not something that can be rationalized and easily explained away. Entrepreneurship is a deep desire to create and destroy at the same time. It requires simultaneous distain for authorities and respect for past artisans. In fact, if I thought there was a cure, I would have taken the blue pill. Therefore if one could accept entrepreneurship as what it really is, then there is a much less immediate need for acceptance and validation (except in the marketplace). The end result is that entrepreneurs would have a very different perspective on listening to unpleasant truth, that rejection is not an undesirable and unavoidable side product, but in fact part of the journey.
It all else fails he can always ask the customer. Just phone the sucker up and start a discussion instead of guessing what they want.
Bill Gates has said something like "Your unhappiest customers are your best sources of learning."