I find this particularly compelling on the lowercase side of things, but I have no issues with the capital B (and when I'm writing with others who use it, I don't put up a fuss):
I can't say I understand (and perhaps it is not a matter of understanding, per se), but I do recognize and feel the affective and political motivations for using the capital, expressed in tweets like this:
I do get understand this, though--if we capitalize nationalities and ethnicities and Black is meant to signal some panethnic identity among the heterogeneous group that we call Black Americans, then this seems to be in line with convention.
This is probably what I would've said prior to reading all the replies, but I might be convinced now that a capital B might be useful to signal a particular, proper thing in some cases, where a lower case b would signal something messier & more terrifying
So, in general, people tend to understand and researchers tend to deploy intersectionality as depicted in the images attached. In these models, categories of difference/identity (race, gender, etc.) are thought to "intersect" to produce a unique social location.
@Much2Blaq Or, in the second graphic, categories of oppression (patriarchy, homophobia, etc.) are thought to intersection to produce a unique social location. By unique social location I mean a significant category of difference (like "working class immigrant man").