Hot take: I've never met a stupid person. I've met irritated people, I've met people whom were victims of circumstances where they've acted irrational, I know far right and nationalist thought, yet I never met someone that I could whole heartedly classify as “stupid” or “dumb”, beyond the colloquial usage of the word.

I've met people victim of circumstance, people who didn't know any better, people who acted exactly like the environment around them was designed to make them act. I also know (mentally) disabled people, and I wouldn't call them stupid.

The people who call the usage of the word ableist in itself are correct. Additionally, I believe it's individualizing a systemic problem and classist. Correct me if I'm wrong or if my train of thought has some inconsistencies, as I'm not so sure what I'm missing here.

Would I not act the exact same way as the person in front of me if I was in their position? Is there truly an inherent biological trait that makes people's general judgement of situations better?

If it's not biological, isn't calling someone stupid hiding the fact that they can educate themselves or generally change, by pretending their incorrect judgement was something inherent to their nature? I see no advantage to that term, rather I think it's doing harm.