Good question: "That is an interesting finding, I'd be interesting in seeing the methodology behind the study."

Insulting question: I wonder if the authors made a certain specific error, when making said error implies the person is either ignorant, stupid, or intellectually dishonest.

I'm not not going to defend the statistic since I haven't seen the methodology. That said, I do think it's insulting to the authors to ask if they've made a very basic and specific error without first reading the methodology.

In any event, I'm sure you could email any of the authors and ask where the statistic came from if you are interested.