What is the author's tone in Food of the Gods: The Search for the Original Tree of Knowledge by Terence McKenna?

The author sets a very controversial tone in the book. He writes using very opinionated language and words to support his ideas and beliefs. For example, this sentence makes several claims without qualifications or irrefutable supporting evidence: "Medieval Europe was one of the most constipated, neurotic, and woman-hating societies ever to exist." Sentences such as these clearly demonstrate his viewpoint and direction he believes the evidence points.