What is "stupidity" other than a concept vague enough that you can just throw it at anybody to, in part, immediately raise yourself to some level of superiority, and essentially defame without actually having to argue anything? Obviously they are stupid, and since you realize that, you are obviously not, so what's there to argue, right?
Human intelligence, if that's what "stupidity" is supposed to be about, is many-dimensional. Even within a single dimension, most actions, opinions or expressions of such are not clear-cut more or less intelligent. Often you just happen to agree with one or see problems with another one. But it doesn't immediately mean somebody is "stupid". And it also ignores the "why". Maybe somebody is lacking education in a certain field, perhaps because of a lack of funds or opportunity because they grew up in a disadvantaged neighborhood. Or because of a medical condition. Or maybe they are just tired. Who knows. Oh right, they are "stupid", that's what they are.
And finally, even if somebody does something "stupid" .. don't put yourself on such a high horse. You likely also do "stupid" things. All the time. You don't realize it though, you'd otherwise stop doing that thing. So, if the conclusion is that we are all "stupid" in some way, they yeah, we can claim that there are "stupid" people all around us, but that's not a particularly meaningful statement.
Honestly, this was a very sad read.