The New York Times reports that a group of deaf actors is opposing the use of a hearing actor in the role of a deaf character in a major stage production of "The Heart is a Lonely Hunter." The hearing man is reprising a role that he has held in earlier productions. The deaf actors argue that there are not enough roles for deaf actors; the producers say they did reach out to the deaf acting community when casting the role earlier. The producers will not make changes for this production, but are open to making changes for a future production.
The deaf community has argued about this before. While it is widely understood that deaf roles are best played by deaf actors, must they always be played by deaf actors? If we say that they must always be played by deaf actors, then does that mean deaf actors should not play hearing roles? "Reasonable Doubts," anyone?

Actually, I disagree. If you look at the situation in context, the character from the novel originally was deaf mute. The playwright re-conceived the character as orally trained. The directors did not try very hard to find a Deaf actor, and they could not find a Deaf actor who could speak well enough for them, cf. “…it was judged that neither could speak well enough to play the part of [the main character].”
I think that is completely ridiculous. The directors thought that Deaf people could not speak well enough to play a Deaf person! This is the decision that is offensive. It is an insult to anybody’s intelligence, never mind any audist considerations. That’s like saying, “We couldn’t find an actor who uses a wheelchair daily that could walk well enough to play Stephen Hawking.” Sure, if you had rewritten Stephen Hawking’s life to involve him walking again, it would be impossible to cast someone with a neuro-muscular dystrophy in the part!
Likewise, the role only needs a hearing actor because the character was wrongly changed from a deaf mute Deaf character to a speaking Deaf character. If they had merely made a casting decision, I might agree with your middle-ground standpoint, but it was a pragmatic decision based on a misinterpretation of a character of classical importance to American Deaf culture. You cannot discount that.