Lennard J. Davis in the Chronicle of Higher Education:
What does it mean to be “not deaf enough”? In Fernandes’s case, the accusation meant that she was not a native signer of American Sign Language (ASL). Fernandes learned to sign later in life; she is best described as a user of Pidgin Signed English (PSE), a blend of English and ASL. So she cannot speak with the “accentless” signs that would read, to a native signer, as the most elegant ASL. In effect, she would be speaking sign language the way that Henry Kissinger, Arnold Schwarzenegger, or perhaps Borat speak English.
Many hearing people would deem any prejudice against someone because of his or her accent shocking and unethical. To understand the issue, you have to know that ASL has become the armature on which the figure of deaf identity has been built. Until relatively recently, deafness was seen as simply a physical impairment: the absence of hearing. In the past, much discrimination against deaf people was based on the assumption that they were in fact people without language — that is, dumb. And “dumb” carried the sense of being not only mute but also stupid, as in a “dumb” animal.
But over the past 30 or so years, the status of deaf people has changed in important ways, as deaf activists and scholars have reshaped the idea of deafness, using the civil-rights movement as a model for the struggle to form a deaf identity. Deaf people came to be seen not just as hearing-impaired, but as a linguistic minority, isolated from the dominant culture because that culture didn’t recognize or use ASL.