Yeah we typically thing age discrimination is saying we only hire people between 20-40y/o but it would also cover it if you said “I won’t hire someone 21 years old only” and still applies to banning someone 21.5 years old. And 21 years and 6 months and 27 days old.
Same applies if I ban anyone with an age divisible by 3. It’s a group of people, but if their age has anything to do with why you aren’t hiring them then I’d say this applies.
I don’t think most people are stupid if stupid means lacking reasoning skills or knowledge or curiosity. You can find all sorts of people who you’d think sound stupid but know tons about one subject. But even if they don’t, they likely have a working knowledge base and only know what they need to know.
What I consider stupid or problematic is that most people, probably 75% or more of the overall population, are not skeptical or analytical and have a fundamentally busted epistemology. Even if your information filter works, if you don’t understand why it works, I’m going to struggle in conversation with you. So yes I think the general population has a hard time thinking critically because they don’t know how to analyze their own beliefs or knowledge.