Just offhand, your "injustice" statement is obviously not true. The little person is played by a little person, for a start. Leslie Neilsen is, and has been for many years, pretty near stone deaf. I'd expect there are plenty of other examples in the cast and crew.
I suppose that depends on whom you ask. Someone who's congenitally crippled from their mom being given Thalidomide may or may not consider themselves "disabled." Local LA newscaster Bree Something-or-other has a congenital deformity of stunted, twisted hands, but she doesn't consider either herself or her daughter (who also has the deformity) "disabled. Bree's made quite a career for herself.
A short person may or may not classify themselves as "disabled." It's certainly an inconvenience to have to reach up to turn a doorknob, or climb onto a step stool to work at a counter. Is it "disabled"? I suppose you'd have to make that decision yourself.
I guess it really does depend on who you ask. Some might view themselves as disabled, while some might just say they're at a disadvantage in certain areas.
GK: Every show is your last show. That's my philosophy. Rhonda: Thank you, Plato.