I like radical (in the radux sense) feminism's philosophy of the identity here. You do not get to truly define a group if you are not part of it. I think it would have been way out of line for Nyad to tell Oprah that she wasnt a black woman as she thinks of it, rather her own definition of a black woman.
Nyad will tell you what she is. You listen. The end.
There's no "well you're not what I would call...."
I like this comment. And you'll notice that this happens all the time when believers don't agree with what other believers do. That guy who murdered people in the Norway shooting wasn't a "real" Christian. The 9/11 bombers weren't "real" Muslims. I think particularly when it comes to religious belief, we must take people at their word, as it is only themselves who can define their own beliefs. I have a friend who often tells me I'm not a real atheist because he just doesn't believe that I'm capable of really not believing. And I'm always like, yeah man, trust me, I'm an atheist. I wish Oprah got this.