It's like the "cure" for the mutant gene in X-men. Saying it needs to be cured can be interpreted as saying "it's bad that you have Down's Syndrome". Giving someone enhanced mental capacity would certainly help them, but I think for someone who's used to accepting and loving others for who they are, it isn't necessarily odd to have an uncomfortable reaction to the idea of "curing" them - even if, objectively, it's helping them.
