I think "mountebank" is an excellent choice of words. Quite possibly different ethic groups do have different distributions of mental ability, but the authors of the The Bell Curve didn't prove it. Their work is practically auto-debunking in that the authors supply everything required to dismiss their own argument out of hand. The central argument is very simple. The claim is that there are only a few well-understood possible causes of the 1-SD observed difference in the average scores for black and white Americans. They examine each carefully and show that none of them can account for a 1-SD difference. Genetics is all that remains, so QED. Uh, except that earlier in the book they spend a good chunk of a chapter talking about the Field effect, which they explain is a cultural effect the cause of which is not understood and which happens to be of approximately the same 1-SD magnitude as the observed difference. But their argument in letter and spirit explicitly depends upon no such unknown causes existing. It's a giant hole that makes their argument a non sequitur. Which brings us to "mountebank." Those old boys are plenty smart enough to dismiss their own argument on this trivial basis or on any of several of the reason Taleb snorts at it. So what other conclusion is there?