That entire book is based off of a false premise about what the word catholic means. In fact the whole treatise seems to be using the word Catholicism as a kind of insulting caricature of all things wrong with religion and then working very hard to backwards ascribe that in history. For the record catholic simply means "according to the whole". Just as one Church is according to the whole Church of Christ.
There's a ton of speculation presented as fact, begging the question, in how they gloss through the history of the church. And lots and lots of scare "quotes" like saying "bishop" even though "episcopos" is a scriptural word.
In other words, that's a pretty useless document, read meat for people looking for confirmation bias, worthless for any other purpose.