It isn't that we cant wrap our heads around eating fructose in whole food form. You could make a case that the book Primal Blueprint would actually advocate a couple pieces of fruit or berries over that of starchy tubers or rice. The disconnect is the form that fructose takes and the quantities ingested. There is no appreciation in the Peat camp for what has produced health in traditional societies from what I have read. It is a theory based on biochemical breakdown and analysis, and is incomplete because of that IMO.
The "look at children" argument makes no sense. My kids have no additional sugars in their diet (I'm sure plenty of Primal parents do the same) and they have all the energy and vibrancy that you seem to attribute to needing such....in fact so do I. Eat more...doesn't matter if its fat or sugar and your metabolic rate goes up (fact).
As far as if your getting your carbohydrate from starch or fruit (if you feel you need it) its quite dependent upon what sort of microbes currently populate your gut as to which you prefer. Seems if your suffering any form of liver dysfunction including metabolic syndrome that you should tread lightly with fructose even in fruit form.