The meaning of fact-filled itself, is simply something that is full of facts—or truths.
In the quotation, however, fact-filled has been put inside so-called scare quotes.
From Merriam-Webster's definition of scare quotes:
quotation marks used to express especially skepticism or derision concerning the use of the enclosed word or phrase
In other words, putting "fact-filled" in quotation marks here means that the author of the quotation is claiming that statements supposedly full of facts are not actually factual at all. Instead, rather than being fact-filled, the statements are full of untruths.
The passage could have been as easily understood if they had not bothered to write "fact-filled" at all, but just left it as "intimidation and untruths." For some reason, it seems they wanted to express an emotional disdain for the authors of the referenced book.