When I read a nonfiction book on a controversial topic, I look to see if the author cites evidence, particularly scientific evidence, that supports his/her point of view. When I read Lakoff's "Don't Think of an Elephant!", I didn't see much evidence in support of his ideas. In particular, his hypothesis about strict father families versus nurturant parent families seemed to me to be plausible but lacking empirical support.

On the other hand, different scientific fields have different methodologies, and I am unfamiliar with the methodology of linguistics. And authors sometimes dumb down books for the general public by omitting the scientific evidence.