As words go ‘stupid’ is a problematic one, and seldom deployed in useful ways. It is usually meant as an insult, and to place responsibility on the shoulders of the person it is aimed at.
If ‘stupid’ is used to refer to someone who lacks the mental processing power, then ‘struggling’ might be a more useful term. If there’s a hardware issue, then what people tend to need is more time. More support, and better support are also considerations. It is not the fault of the person who can’t keep up. The onus is on everyone else to make it possible to keep up.
If ‘stupid’ refers to a lack of knowledge and education, then this is something most likely beyond a person’s control. Poverty, family background, racism, sexism – these things often contribute to a lack of educational opportunity. It’s hard to learn if you’re hungry, if no one takes you seriously, if you’ve got bigger things to worry about… If the problem is a lack of information, the onus is on the people who know to make that information available and accessible.
If ‘stupid’ is used to refer to a lack of wisdom or common sense, it is worth bearing in mind that this is subjective territory. We can all be wise in hindsight, and the more experience we have the more we might be able to predict things. Education can be a factor here, as can exposure to misinformation. It’s worth remembering there was a time when wise men knew the earth was flat and only stupid people thought it was round. Wisdom is subjective.
Intelligence is not a single, all encompassing quality. I have a good head for words, but very little visual intelligence. Some people have stupendous physical intelligence. Some people have incredible mathematical intelligence. Some people have academic intelligence but not much handle on day to day life. Calling someone stupid because they aren’t clever at the thing you are clever at, or at the thing you want them to be clever at usually dismisses what it is that they are clever at. Most people do have areas of strength and ability if you have the inclination to look for them.
When people with power want to manipulate people with less power, they can do so by turning ‘stupid’ into a virtue. If experts are suspect, evidence is fake news, and opinions matter more than facts, the will of the people can become a really toxic idea. Communist China did it. Contemporary politics in the UK and America is trying it.
One of the most popular uses of ‘stupid’ is to denigrate someone who disagrees. It’s a simple enough process, trying to imply that the truth is self evident and therefore something must be wrong with anyone who doesn’t see it that way. However, if you want to seem clever, defending your position with logic, evidence and clear arguments is a good deal more convincing than putting people down. The person who calls others stupid is setting themselves up for similar treatment, which isn’t an especially clever course of action.
Then there are the people who refuse to learn, or to look at facts and evidence. The people who won’t hear and won’t know and think their opinion is worth more than the evidence. The wilfully ignorant. The people who have bought into a story so entirely that they cannot bear to have it challenged. The people who can’t face the truth and so wrap themselves in lies to be able to cope. The people who gain more from lies, and who may lose their advantages were the truth to be more visible. Sometimes, some or all of the above issues apply to them. The rest of the time, it’s not effective to call them out over their intelligence. Instead, we have to call them out over what they are doing. Keep pointing at the evidence.