I find the author take on this more problematic than anything else. I deal with disabilities daily, I know what it’s like, feeling that the world was carved to weed you out. I also know what it’s like being expected too much, enough to know not to place unrealistic expectations upon people. People do not know enough about people with disabilities, I’ll agree with you on that; but the instances you used to prove your point do not represent reality fairly: a cashier register might speak to someone with a disability slower and louder, not out of spite, but because she believes she’s reaching him on a “fairer” level. Would you speak the same way to someone who is learning English — has very little knowledge — as you would someone more proficient in the language? This brings to mind that people are not ignorant of disabilities, but not informed enough. Maybe the cashier thought the individual to be intellectually challenged, one of the disabilities we’re more familiar with, that has a well-seated place in the book of insults. My point is, these are not deliberately-hurtful acts. We’d benefit more from a more balanced, sympathetic of both parties, discussion.
Also, I’ve seen more than a couple of instances where people get vocal about a baby crying in public; I’m afraid you were wrong with that one too. I’ve seen people get angry at “normies” being obnoxious in public too. While I’ll personally express my disapproval quietly — as, in the case of a baby crying, I know it can’t help it . I would react this way too, toward someone with disabilities, as I have in the past— you can only expect so much from people, especially when there is nothing at stake for them.
We need to thread this matter carefully, and realistically.