You don't understand the concept that we should expect credible evidence before accepting something as fact. And you don't understand the difference between asking for - and pointing out the failure to provide - said evidence, and telling people to shut up.
I'm not surprised.
That was not a peer-reviewed scientific study.
It was not a PhD thesis in anthropology.
Nor was it a PhD thesis in biology, or psychology, or even sociology.
In fact, it wasn't a thesis in any scientific field at all.
It was
a PhD in Public Policy.
But you must know that. Undoubtedly you have already read the thesis; your linking to some fourth-hand opinion piece by an online blogger is merely clever camouflage to lull us into a false sense of security. Despite it not being a scientific article, you are confident that it contains sound scientific data. So please, tell us all about it.