Asklemmy

Not learning and adapting, never admitting they're wrong when they actually do realise they are wrong.

Managers tend to not like me.

People who believe in the bible as a historic document.

Bigotry

It isn't necessarily about intelligence, since stupid is as stupid does.

I tend to call that willful ignorance. It's knowing that there are other ways of thinking, but refusing to even consider them. Which is stupid, dumber than dammit, and/or moronic. I've known some damn intelligent people that are stupid by virtue of not using their brain.

Be aware though, not everyone can control their volume. I don't doubt you were aware of that, but it's not so rare a thing as to not be worth mentioning. There's also others that have trouble controlling volume.

Again, I don't doubt you meant the folks that can control their volume, and do so without difficulty, just adding to things.

Not keeping a constant speed when driving on the highway. Just pick a speed and drive.

Above everything, lack of curiosity. If someone is uncurious, it's a big red flag to me.

Inability to see things from different perspectives. Assuming any perspective you talk about is your own personal belief.

Anyone who refuses to change for any reason.

Conservative politics, as Mill points out, stupid people are attracted to it. Many of them will plant a sign on their lawn to let you know.

"I did not mean that Conservatives are generally stupid; I meant, that stupid persons are generally Conservative. . - John Stuart Mill

I will counter that the definition of intelligence is needed. Yours OP seems to be emo intelligence, maybe social intelligence. One can be very intelligent in other areas while not within these.

My quality would be a person's ability to abstract and understand subjects through inference and intuition; to see all the layers of bigger pictures and the uncertainty of truth when contextualized.

In many ways, I fail at my own stupid, but it is a striving in life. After all, what use are achievable goals.

Stupid is subjective, circumstantial, and non binary.

for no reason

Just for the sake of argument, one good reason is actually something I dealt with for a while there: after having worked in a factory where hearing protection was absolutely mandatory for close to a year, for like two years after leaving that job I found myself shouting, even indoors, without even realizing it. It had just become second-nature.

My point is even if there doesn't seem to be a reason, there might be.

Edit: Just to be clear, it was a job where hearing protection was mandatory, and I was there for close to a year; it wasn't only mandatory for close to a year. Lol.

When they don't use their indicator signal.

Religion of any type.

Some people aren't self monitors. A lot of stupid/ignorant people are loud, but being loud can also be lack of awareness of their volume, hearing deficit, or cultural

Maybe they're hard of hearing and don't know.

I have really bad social anxiety and will either speak too quiet or too loudly when i have to talk to somebody, there's other reasons someone might speak too loud.

You talkin shit about Ranger Carl?

I've always valued privacy when having a conversation in public. I speak loudly enough for the person I'm with to hear me. I've never understood people just yacking loudly so the whole world knows their business.

Loud college students were having a conversation behind us yesterday (the museum is near the university). I stopped and my partner was stopped by us holding hands. Waited till they got about fifteen feet in front of us and resumed walking.

For me it's more likely that they just grew up in a big family where you can't get a word in unless you speak up

Yes that's a good one. I'll add table manners. If someone eats with their mouth open I'll instantly think a lot less of them.