While visiting the ruins of Ephesus in Turkey, Dalrymple notices a sign using the term “vision-impaired”. Judging from the context, surely they meant blind. So why not use that word?
Calling the blind vision-impaired requires no actual kindness or generosity toward the blind, no actual generosity; on the contrary, it is perfectly compatible with complete indifference towards them. The blind are a small minority in the world, while those who speak are the immense majority (apart from the speech-impaired, who are often hearing-impaired as well). To interfere in the lives of everyone, to make every person just a little afraid that if he uses normal words he commits an act of cruelty or worse, gives a sense of power and meaning to those who demand that we change the way we speak.