I feel like an arsehole because I get freaked out by disabled people.
It happens. I feel like an ass because most of the men in my life can tell I'm afraid of them, even when it's very irrational.
Long ago at my agency, a nurse was unpredictably attacked by someone she was attempting to give care to. He stabbed her through the eye with a pencil. She wound up needing all kinds of medical care, lost the eye, developed PTSD, and could not work anywhere near that field again.
None of the people who work with me get into it disliking the disabled. I would bet she did what she did because she loved that environment. But trauma makes fools of us all, breeding nonsensical fears and laying waste to our trust.
I agree with
@Pencil; sibling abuse is under-acknowledged and gains little attention in the public eye. A lot of the invalidation I have encountered around sibling abuse is the mantra "Kids will be kids" and variations thereof that essentially state siblings can't abuse one another, because sibling problems are universal and non-traumatic. There is a very serious difference between expected horseplay or rivalry and malicious ongoing physical, mental, or sexual abuse by a sibling who is somehow more powerful than the other (especially in terms of age, size, and parental favor).
My brother is not developmentally disabled, although if you asked my mother about him, you might get a strong impression that he is. She has (especially now that he is in his 30s) framed his shortcomings by incessantly pointing to mild learning disabilities. Story of my life. My poor, stupid, incompetent brother needs to be coddled and taken care of, nevermind how vicious, malicious, manipulative, selfish, and remorseless he is. I could not imagine if it were true that he had an actual disability with which she could attempt to justify his abhorrent actions.
Having worked with this population for over a year and a half, I can say with confidence that one can distinguish harmful behavior that arises out of not knowing any better or not being able to help themselves versus malicious intent, and it's hard to explain to the general public that there is a difference. The public would, by and large, like to discredit and infantalize the disabled community by assuming they simply know nothing rather than to admit that they are like all people: a constant shifting dynamic of good, bad, sweet, and nasty. Such is the mercurial nature of human character.
