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The question "would you accept this from a male writer?" doesn't work. The thing about gender politics is that gender is always relevent. Coming from a man, this topic would likely be an issue of objectification. Coming from a woman, it's an issue of identification. The underlining messege is "I never expected somone with my physical characteristics—i.e. a black woman—to be First Lady." That idea is conveyed with pride in the beauty of the writer's own race, a form of beauty often marginalized. Specifically black characteristics are "urban." In otherwords "ghetto." To be "refined" is theoretically to display white characteristics. Which is, of course, nonsense.
A male equivalent would not be about Barack's package, but more likely, "I can't believe someone with my flared nostrils" or "my crinkly hair." Because again, as unpleaant and uncomfortable as it is to bring this us, the fact is a lifetime of socialization has taught us that people with these physical characteristics don't get into power. That article wouldn't be as funny, because those black male physical characteristics haven't been turned into a sexual plus the same way a large butt has. But the essential point would be the same.
I mean, come on, look at the number of black models, actresses, etc. who are famous, yes, but look more like white women with a deep tan than like African Americans. Michelle Obama is not one of those kinds of women. She represents a kind of beauty specific to black culture, and that has appeal to the black culture (but not necessarily only to that culture). The article is about pride and identification, not about reducing the First Lady to her ass.