The mom of a disabled child explains that she always thought it had been learned at home, but having seen her own children, who never knew a world without Cherub (their daughter), become prejudiced, she says that prejudice is a natural response to something “not fitting.” It’s an excellent blog entry and very engaging.
A short version is:
As time went on, I noticed something that broadened my understanding (and revised my judgment). Some of these children had been happily playing with the Cherub since babyhood. She loves babies, and smiles and coos at them. She likes to hand them toys (and hug them too hard, so we must be careful). The babies love her back. But at some point, as the babies grow into toddlers and preschoolers, nearly every one of them we have ever known will reach a point where they are afraid of her. I can only guess at why from my own personal observations, and that’s not conclusive, but I think I’m right. Here’s what I think happens- at some point the babies grow up enough to have a certain understanding of how the world works and how people act and what they are supposed to do, what is familiar and what is not- and at about that stage in their development they notice that the Cherub does not act like everybody else, and she does not respond to them like everybody else, and they do not know why, but she’s very different- and it makes them uncomfortable, nervous, frightened, or just strongly unsettled. They don’t like this, so they avoid the Cherub and want her to leave them alone.
But I recommend you read the whole thing.