Beards answer points out among other things that there are exceedingly few traces of Normans in the genetic record as well, and gives a plausible suggestion that most might simply have left, like the Normans did. She also points to more examples than a single Ethiopian conscript.

So the reality is that we know there has been people here that are poorly reflected in the genetic record, and that makes it rather pointless to point to the genetic record to demonstrate the family in question is implausible.

In any case, what troubles me much more than whether or not the depiction is plausible is just how incredibly unprofessional and rude Talebs reaction was. If he wants honesty and a focus on the science, he should grow up and act professionally.