You are misrepresenting the author. He made no such claim. He did not articulate what he believes the underlying mechanism to be.
It would be perfectly reasonable to inquire about the mechanism, or question the accuracy of the prediction. It is not reasonable to make accusatory conjectures about his beliefs.
The blogger is repeating (with citation) a claim by Richard Lynn, and by the end of his life Richard Lynn was open about being a 'scientific' racist who believed that different races had genes which caused large differences in average intelligence
You are misrepresenting the author. He made no such claim. He did not articulate what he believes the underlying mechanism to be.
It would be perfectly reasonable to inquire about the mechanism, or question the accuracy of the prediction. It is not reasonable to make accusatory conjectures about his beliefs.