There are, of course, a slew of new editorials out which purport to explain the difference - the identity politickers of the Left are tying themselves in pretzels to justify transgenderism while decrying transracialism, even though they have made this bed:
Anyhoo, the difference between how the Left treats transgenderism and transracialism is both simple and obvious.
Rachel is a villain because the Left does not believe in
black brains (or at least - they know better than to admit such a belief.)
Bruce is a hero because the Left does believe in
lady brains.
What's the difference between the idea of black brains and the idea of lady brains?
"Black brain" erases the experience of racist socialization. Some men experience racist socialization, so that experience cannot be erased.
"Lady brain" erases the experience of feminine socialization. No men experience feminine socialization, so that experience can be erased, with glee.
This is also why we can have
an essay on how Rachel Dolezal is not a black woman because she did not grow up as a black girl, when
no such standard holds for Laverne Cox or Janet Mock.
HTH!
[More thorough take on this issue here: Sex and Race and Boundaries on the Left.]
Editing to add: For those asking why Dolezal couldn't work for civil rights and socialize with black people as a white person: 1) I agree, and 2) Why are we not allowed to ask why Jenner couldn't simper in expensive lingerie on a magazine cover as a man?