My dad had a prosthetic leg, and he bristled at some of the polite or accepting ways that people would talk about disability in a way that stuck with me because he explained it. Basically a dislike of "handicapable" or the notion that you "make up for it" in other ways. To paraphrase: "getting my foot cut off in a car accident didn't come with some perk that balanced things out".

I think a lot of the pushback you got came not from a place of rejecting that they could have a bias, but from the topic being broached as a confrontation of bias instead of an explanation of ignorance.
People, like the poster above, who are being conscientious according to their understanding will get indignant or frustrated when that's met with an unmatched response.

Assuming positive intent colors implicit "positive abelism", or other "positive -isms" that I'm personally less knowledgeable about, as unfamiliarity or ignorance rather than callousness or rudeness.
In those cases, the person is very unlikely to disagree or pushback if informed about their blind spot. The key part in their head was "disabled people are just as important", sitting right next to "good people chip in and contribute". So they respond to "disabled people can't always contribute" with "disabled people are important!" phrased as "disabled people can contribute!”.

Addressing it as a bias against disabled people doesn't fit because that part is correct. Need to address it at where the problem is: a misconception about the relationship between human worth, labor and utility.