Southern,
I think you missed gnu's point. He is not claiming to know what it is to be deaf. He has never claimed to be a deaf individual. He is making the point that Deaf culture is based primarily on linguistic considerations. One's language determines cultural norms and values. He has experienced Deaf culture by proxy through that linguistic avenue. As have I as the mother of a Deaf son. I do not know what it is to be without auditory function. However, having been exposed and participated in Deaf culture, as well as having raised a Deaf child, do have an empathy and an understanding of what it means to rely on the visual for interpretation of the world around one. Further, having served as my son's advocate for 18 years of his life, and continuing to do so in some situations today, I have an understanding of the difficulties experienced by misperceptions by the hearing community regarding those who ID as Deaf and rely on ASL as their primary communication mode. As a signer, I also understand the differences in perception that are the direct result of linguistic differences, and have spent a great deal of my time attempting to explain those differences to many hearing people. Dealing with deafness on a daily basis in an intimate way does not make one deaf, but it does allow one to gain insight and perspective that most hearing people are unable to achieve by encounters with deafness from the outside parameters. My home, for instance, is the home of a Deaf person, because it had to be that way for my son's benefit. As a consequence, my experience more closely relates to the experience of the Deaf than one who has not modified their daily life to accomodate deafness.
You are correct in your statement that no one can tell you what it is to be a gay man unless they are gay themselves. Unless you are gay, those experience are not internalized and do not become a part of your day to day existence. However, straight individuals can, and many do, empathize and understand what it is to be a gay man in a straight society.