I feel like it's worth noting that admitting you're wrong or using ableist language is HARD, but it's part of the growing process. the fact is, at some point in time, I'd be willing to bet that all of us have used ableist language at some point and then learned why it's harmful. I'm thinking in particular about words that were "cool" to use in like, middle school or high school. or, language I used two weeks ago that I didn't know was ableist, and now I do.
There's nothing wrong with making a mistake, especially if you didn't think of it as harmful. Most people don't call someone stupid and think of it as making fun of a disability. They say it to make a point. But I'd suggest everyone reading consider this – we don't know each other in real life. You don't know if someone is struggling with something, and for all you know, whatever word you're using is the same word kids used to make fun of a comrade when they were younger, or even as an adult. Just be mindful and think about the impact your words could have on ANYONE reading your posts/comments. Think of all the slurs you wouldn't dare use and the reason you don't use them. Then think about other words that could have the same effect, but just aren't as accepted necessarily as "slurs" in general society.
Side note, making fun of someone's intelligence also suggests that someone who may have an intellectual disability or even just be neurodivergent and not think the same way you do has opinions of lesser value. While yes, you probably don't mean that with your words, it contributes to a stigma that benefits no one.
TL;DR: think about the person on the receiving end and write what you actually mean to tell them, not the insult you shout when you're mad/frustrated