While its not my personal preferred style, the NY Times has recently adopted this style (from an earlier one which capitalized neither) and explains it reasonably well (and other explanations of users of the style have generally been similar, so its what I take as, in outline, the usual explanation):
https://www.nytimes.com/2020/07/05/insider/capitalized-black...
Thanks, and yikes, I had no idea this was a thing. So if I wrote "White" in the same way some might write "Black", people might get the wrong idea? To be honest, this change just seems like more petty ways to divide us.
There is no “like no one else does”; the argument is that Black identity (particularly in America) is essentially an ethnic identity produced by shared experience, the same as other ethnic identities. The distinctive part is that the shared experience centrally includes American White supremacy which, among other things, actively erased the preexisting ethnic identities of the black people whom it made Black.
If you look at it from a people perspective, it doesn't make sense because people want to be their own individual, not lumped into a category because everyone experiences things differently. I see this as an artificial construction that is usually argued against.
There are certainly similarities, but then, no one denies that “Jewish” is a national/ethnic/cultural identifier that should be capitalized, even if racial or physically descriptive identifiers generally shouldn't and even if “Jewish” might also be considered a racial identifier.
There are arguably even closer similiarities with the various peoples with roots in the pre-Columbian population of the Americas. But, again, whatever label is used for various collections of those people, one rarely sees arguments against capitalizing the label chosen.
Identities are arbitrary, but they aren't ethnic unless they are rooted in an ethnicity, which is a shared culture.
Because, the best cure for perceived systemic racism is _actual_ systemic racism. It's all absurd.
What is sad is when people hide in the shelter of group identity, instead of being responsible for their own speech and actions. It's often not in anyone's best interests, and distracts from clarity.
Slavery, oppression, and loss are not the only ways in which a shared culture can be formed.
No, that they share an identity forged in the experience of slavery and the discriminatory laws afterward, and in many cases that's all the ethnic identity they have because their ancestors preexisting cultural heritage and identity was forcefully prevented from being preserved.