So, you seem to be saying that Yvain is using Watson as an example, at least partly (and significantly so) in order to convince others of (not to put too fine a point on it) the racist IQ hypothesis.

I had a different reading of the post, which was that even for someone who disagreed with the racist IQ hypothesis, Watson's pronouncements should carry more weight than a random person's. I actually agree with Yvain - though I also note that looking into Watson's actual argument in even a little more detail was enough for me to dismiss it.