The entire second section is about sugar/grain lobby shenanigans that took place decades after public officials started recommending fluoride (1961 and 1979/1986/1994 for American Heart Association and American Diabetes Association recommendations vs. 1940s for fluoridation recommendations). The diet recommendation reversals came more than a decade after fluoridation became public policy in the US, but they're presented first as an attempt to confuse the order of events for the reader.

I read the article. It's... not good. It relies on semantic trickery and intentional obfuscation to make its points. The parts that aren't nonsense ("sugar is terrible for your teeth/heart/diabetes", "fluoride would be less necessary if it weren't for excess sugar in popular foods", the actual record of events, etc.) are neither novel nor disputed.

Regardless, this belongs on /r/history, rather than /r/science. It's literally just a historical study citing snippets from other books and paper about events 50 years in the past, with 0 original research.