In other words, McGraw-Hill bought them off and discredited independent sources.

I don't think it requires being bought off to understand that a research paper should rely on primary sources and original thought where possible. Obviously incorporating analysis of those sources and potential biases is important, but you want to be able to form your own conclusions based on unfiltered information. Otherwise it's not really a research paper, more just a summary or review of other people's research.

No professor worth a shit What tell students that a textbook is peer-reviewed. They aren't.

I think the idea was that authors / professors of textbooks have a reputation to loose if they publish bullshit. Like they are the authority on a topic and if wrong they loose that status / prestige.