This fellow is shocked, shocked! that when historians read a text, they think about the circumstances of its production, the reliability of its author, the viewpoint of the author and so on.
Real 'couldn't make it through World Hist. 101' energy, honestly. 1/
This is why classicists learn nothing from the classics. Guys like this would see a geology textbook and say “Somebody deliberately wrote this to teach me about rocks. Nice try!”