I prefer to not think about it as stupidity, but vulnerability to manipulation and exploitation.
People are “stupid” because they are misinformed be it through intentional malice, accident or general incompetence.
Identifying people as stupid doesn’t help anything. What needs to be identified is why they are stupid; who has misinformed them, to what end and how can it be combatted.
“If you call someone stupid, there you’ve called them a name. You haven’t actually done anything.” - Zen and the Art of Motorcycle Maintenance