Earlier quoted context omitted.
It's very stupid, but I check dictionary definitions in an incognito window because I'm horrified of someday people coming across my browser history and thinking "Wow, he didn't know the definition of that ?! What an idiot!" The idea of a dictionary that tracks my searches horrifies me in a silly way. Ha!
Looking up words is not stupid. Misusing words because you assume you know what they mean, that is stupid.
Misusing words may or may not be stupid—without more information, including some nebulous stuff about intent and interpretation, I have no way of saying for sure in a given encounter.
What I would say instead is that many people seem to see “misuses words because [cocky/pretentious/know-it-all/careless]” as a heuristic for stupid. It isn’t a great heuristic, but knowing that people use it to rank you and choosing speech accordingly…isn’t stupid.