People want to eat their cake and also have it. On the one hand “we’re individuals, don’t look at us as a stereotype” (agreed), on the other hand, we share the same culture and history like no one else does, we’re one identity! (This is categorically wrong given the diversity in Africa).
I think the "shared history" part has as much to do with slavery and racism in America (and probably also Britain and Western Europe), which is/was definitely a shared common experience.
> on the other hand, we share the same culture and history like no one else does
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.
I think one could argue much of the Jewish diaspora also have a "shared" experience in a similar way but I don't see the same tension there, though maybe I'm just not seeing it. There are also African immigrants who would have a different experience, even people from the Caribbean have a totally different experience.
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.
> I think one could argue much of the Jewish diaspora also have a "shared" experience in a similar way
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.
Ethnic identities are not "produced by shared culture and experiences", they're essentially arbitrary. The modern "White American" ethnic identity was pretty much patched together by early 20th-century Progressives (certainly diminishing the "preexisting ethnic identities" from Europe, though of course not "actively erasing" the bulk of them as the slave trade did to Black identities!), but it would be clearly wrong to suggest that many Americans don't identify as a result with being "white", at least in a subculture-related sense that one might very well call a source of "shared experience" and continuing ethnogenesis.
