Interesting point! But perhaps an atheist would object that what you called "macro-whys" are entirely different that what you called "micro-whys." Perhaps they could argue that macro-whys are silly while micro-whys are not.
Having watched the debate, and considering that Dawkins dismisses "why" as a fundamentally silly (meaningless) question, one would have to ask how such a mode of inquiry ("Why") would ever have evolved within a system wherein it had absolutely no relevance? This is especially true by degree as we realize how "why" inquiry occupies the minds of most people as a critical mode of inquiry and one that exists within us as a deep desire for satisfaction? From the perspective of evolutionary theory, "why" would most of us even want to know "why", or even have the ability to consider the why question, in a universe that only exists in a materialistic fashion wherein such questioning serves no purpose? If one answers that there are proximate, circumstantial reasons why "why" has evloved , ("Why" did that person die when they fell from the tree to the ground", has survival value), then you've let the cat in by the back door. Now why is very releveant, and the natural extension of that is to extend it from the small "whys", to the larger "whys" within the human mind. In fact, it is inevitable that we would ask those macro "whys". So you may disagree with whether there is a satisfactory answer avaiable for the macro "whys" (and certainly there isn't one possible from science alone, or at all). But even from an atheist viewpoint, you can't call the "why" question silly. It is inevitable.