Regarding the reasons for this, I'll repost:
Being deaf is an inherently negative aspect. You either have the ability to hear, or you do not. If you do not, it is a dis-ability. No one wants to lose an ability to do something.
Someone who lives an extensive period of time without an ability may have learned how to live without this ability. They learn to cope and affirm their life with its faults in their current state. Offering the ability they lost and have learned to live without may be declined because of the affirmation of their life as it is. It could be declined because the transition is uncomfortable as well. Either way, being deaf is still negative, they've just psychologically coped well.
If you had the choice, would you choose that your child be deaf or not? That you be deaf or not? If one isn't deaf, would they choose to become deaf or not? This entire argument results from academic nonsense that anyone outside that context can see through.
Regarding culture, culture is defined as "the customs, arts, social institutions, and achievements of a particular nation, people, or other social group.". A social group of veterans (injured or not) absolutely can be considered equivalent as your usage. Preventing war is a cultural genocide if you consider it that way. You're saying that a culture which arises from suffering, injury, evil and so on deserves preservation by refusing to prevent the evil that causes them. Alcoholics Anonymous has a culture, Gamblers Anonymous, etc.
Yes, it is academic nonsense based on semantics. It doesn't matter if they don't feel they're missing anything - what you've never had you cannot miss. What you've had, lost and coped with you've learned not to miss. No one buys into this pedantry but academics with too much time on their hands.
EDIT: I apologize for "proselytizing" and "trashing" that view. My sister is an ASL teacher and she's made the same points you have to me, so I'm aware of the debate, and so have strong views on the matter. I have heard and considered everything you've said beforehand. I believe this sentiment comes from empathy and affirmation of deaf people as taught by those who are close with that community. Yet, I also believe this view is nonsense that someone outside that context can clearly see.