I'm not sure if this makes sense, but it's been bubbling up in my head, so let me try to put it into words. (And I actually started this on Wednesday, before the latest furor about Manning, if that matters. It was sparked by something entirely separate, a dismissive little circle-jerk of people complimenting each other on their correct attitudes about "yellowface" and similar things.)

If you're relatively modern and thoughtful about such things (which might require being relatively young, or relatively to the left side of the political spectrum), you generally believe that gender is not defined by birth -- that there are trans people, and intersex people, and various other permutations. That doesn't mean that a person can choose a gender, but instead a belief that gender is somewhat socially defined and to a large extent a matter of presentation. People thus present themselves as close to how they see themselves as they can, or as close as their society allows them. That may entail surgery, or clothing choices, or anything in between.

And so it's generally rude (at best) to insist that a transman is "really" a woman, or vice versa -- that person is the one to define that label, not any third party.

(And I broadly agree with that; it's not always that simple in real life, but treating someone as the kind of person they want to be and are trying to be is usually good manners.)

But people who believe that also seem to believe that race -- which is vastly less biologically defined than gender is, to the point of being entirely socially constructed, from the ground up -- is immutable, and "passing" as another race is one of the worst things an actor (for example) can do.

So there seems to be a weird mental disconnect -- a white man, for example, is much more "white" than he is "man," even though that's the precise opposite of the biological realities. I'd get it if the racial component were clearly political -- rooted in wanting some kind of authenticity, and demanding that -- but it seems to be reflexive, like a prejudice or the reaction to touching a hot stove.

My question is: if it's fine for a person of one gender (by birth or upbringing) to present or play or act as another gender, why is it wrong for the precisely parallel act when it comes to race?