I've always seen this story, less as a parable about our treatment of the disabled (or the gifted), and more as a lesson about envy. It shows what happens when you try to eliminate envy from society by bringing everyone to the same level, so that nobody has any "unfair" advantages.

edit: I think the telling line is:

> their faces were masked, so that no one, seeing a free and graceful gesture or a pretty face, would feel like something the cat drug in

The point isn't to make people equal for the sake of an abstract egalitarian principle, the point is to stop anyone from feeling envious.

edit 2: There is one obvious problem with this attempt to prevent envy. When you handicap someone, if the handicaps are visible, you can still tell by looking at the handicaps who has the greatest talent, as happens in the story. A more dystopian version would make the handicaps invisible.