I’m talking about derogatory terms like “nerd,” “geek,” “wise-ass,” and so on, as well as sayings like “nobody likes a smart aleck.”
It seems to me that these terms and expressions are used much more frequently in the business world than derogatory terms like “show-off,” “charlatan,” “fraud,” and so on.
I can’t even think of a commonly used saying for the latter. Only: “Fake it till you make it,” which is really more of a reinforcement of the idea that knowledge isn’t very valuable.
I thought you were looking for disparaging sayings about know-it-alls who weren't actually as smart as they made themselves out to be, not just disparaging statements about actual intellectuals.
In that case, I only hear people grumble about people thinking they know everything.