I haven't paid a lot of attention to the debate, so I can't give you a citation. But there have been many claims over the years (some of them by real linguists

I haven't paid a lot of attention to the debate, so I can't give you a citation. But there have been many claims over the years (some of them by real linguists) that language property X is correlated with physical/ social/ ethnic property Y. This "grandiose idea" that you're referring to was one of those, and not one made up by the authors of this paper.