I’ll go with the low-hanging fruit: Mein Kampf. I’ve read it, cover to cover. As a piece of propaganda, it’s good. As an example of good writing? Absolutely not (though I will admit I have only read it in translation). Oh, and the whole fascist, racist, and generally shitty worldview of the author that he infuses into the text. And the fact that the author is literally Hitler. You 5-star that book? You’re a Nazi. Period. And as a Jewish person, I don’t look too kindly on them.
Atlas Shrugged. Virtually everyone I’ve ever met who says they love Ayn Rand hasn’t actually read anything of hers, so if someone had rated it 5 stars I’d assume this was just their way of signalling their political views.
I’d probably react the same way to a 5 star review of 1984, which gets used as an identity badge by people who not only haven’t read the book but who seem to think Orwell’s politics were the polar opposite to what they actually were. I might not swipe left immediately. I’d try asking for their opinion on Homage to Catalonia first.