This is particularly annoying when you really like the book in question, except for that one tiny part that bugs the hell out of you.
I had this happen recently with Sheri S. Tepper's ecofeminist fairy tale Beauty.
In that novel, the heroine is part of a plan to avert a horrible, dystopian future and the end of all non-human (and, eventually, human) life on Earth. Because this is a fairy tale, doing this also involves protecting and conserving less concrete things like beauty and magic, which vanish from the world along with wild Nature.
Here is her appraisal of the situation at the end of the 20th century:
We have been thwarted at every turn by god. Not the real God. A false one which has been set up by man to expedite his destruction of the earth. He is the gobble-god who bids fair to swallow everything in the name of a totally selfish humanity. His ten commandments are me first (let me live as I please), humans first (let all other living things die for my benefit), sperm first (no birth control), birth first (no abortions), males first (no women's rights), my culture/tribe/language/religion first (separatism/terrorism), my race first (no human rights), my politics first (lousy liberals/rotten reactionaries), my country first (wave the flag, the flag, the flag), and, above all, profit first.There, you see it? Right there, in the middle of a fairly interesting attempt to connect the dots between capitalism, patriarchy, jingoism, war and ecological devastation is an unexamined ableist assumption: that, if women were free to give birth, or not, as they chose, none would choose to have a non-neurotypical or -physiotypical baby.
We worship the gobble-god. We burn forests in his name. We kill whales and dolphins in his name. We pave prairies in his name. We have retarded babies in his name. We sell drugs in his name. We set bombs in his name. We worship him everywhere. We call him by different titles and commit blasphemies in the name of worship.
We were given magic to use in creating wonder, and the gobble-god has sucked it dry. His followers reject mystery and madness and marvel. They cannot tolerate questions. They can believe any answer, no matter how false, so long as it is a certainty nailed firmly onto a cross of money. They yearn for the rapture to come, without knowing they have killed rapture forever.
This, besides resting on some very ugly assumptions about what sorts of people there should be, also ignores the possibility that some of the women who give birth are themselves "abnormal" in some way, and might rather have a child who is like them than one who is not.
I also felt personally assaulted in a weird way by that line --- yes, even though I'm not intellectually disabled, I do tend to take the R-word personally; most of the teasing I would get as a child was for seeming stupid, out of it, too naive, or too "young" mentally, rather than for being weird, crazy or awkward --- and I think I reacted to it a lot more strongly in this book than if it had been in another book, a book I liked less, or that didn't speak so clearly to very deeply-held values.