I don't think he's saying selling is bad... but that the goal is to build something great. If you believe in it and are driven by your vision of making it great and you succeed, people will want to buy it. Then you'll have options.

If the goal is just to build something that will get bought, you might be able to get... stressed and frantic about that. But you usually won't have the same type of passionate, intrinsic motivation that drives founders who are in love with their idea.