Dueling moral high grounds
This is a case of dueling moral high grounds. The Authors Guild are pressing the cause of authors' rights to make more money (in theory). The Reading Rights Coalition and NFB are advocating for the equal rights of disabled people. How does society choose between competing moral high grounds?
I don't know of an algorithm for this, but I do know how people think. And, the Authors Guild is suffering because the NFB and Reading Rights Coalition has done a great job of articulating the differences. My take:
Authors Guild: we want to insist that publishers turn off text-to-speech so our authors can make more money over how much they make from the standard text ebook. But, we'd be happy if they charged extra for text-to-speech or required all blind people to register.
RRC and NFB: we can't read the book if the TTS is turned off, at all. So, you're denying us our civil rights. It's not fair to make us pay extra to be able to read if we're disabled. And, registration of disability won't solve the problem of many people who aren't blind (perhaps they have disabilities that fall short of the traditional copyright exemption definition of disability).
The Authors Guild has lost the framing debate. The RRC's motto is "No Need for Greed! We Want to Read!"
So, your average person goes: if I support the Authors Guild, it means that they'll be turning off reading for disabled people. If I support the RRC, it means that disabled people will pay the same amount for a book as everybody else, and the authors won't get as much money as they want.
Which would you choose?