Well, by their logic, they'd want someone deaf, mute, and blind who only learns to speak one word during the rehearsal process...
Logistical question, though--when did these groups start to become so vocal and adamant? I don't remember any controversy surrounding the Swank revival of
The Miracle Worker, which had a hearing actress as Helen. Nobody is up in arms about the fact that the kid in a wheelchair from
Glee is played by a non-paralyzed actor.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body