This would seem to undermine a key tenet of Khalidi's worldview: his insistence that the Palestinian people have a long history.
In a New York Times review of Khalidi's recent The Hundred Years' War On Palestine, Scott Anderson summarized the professor's thesis: "the Israeli-Palestinian conflict is best understood as a war of colonial conquest, one that closely hews to the pattern and mind-set of other national-colonial movements of the 19th century."
So, on the one hand, Khalidi claims all nationalisms are artificial constructs, while on the other — the central thesis of his book and much of his previous scholarship, in fact — he argues that Palestinian nationalism is an inviolable concept threatened by phony Zionist colonialism.
If nationalism is a construct, then all forms of it are artificial, including Palestinian nationalism.
An obvious weakness with Khalidi's thesis is that for it to be valid, he must deny over 2,000 years of Jewish history in what is now Israel. Yet this history is regularly confirmed by new archaeological discoveries.
Khalidi's intellectual inconsistency undermines his own scholarship while denying over two millennia of widely accepted history. Hardly convincing, but very convenient.