Being that all is one, pro blackness is a state of loving yourself whether you are black, white, Asian, Indian, etc. It is the (conscious or unconscious) recognition that this flaw of society (white supremacy) is causing all the other flaws and uses its opposite to remedy it. The fact is, lifting up black people will lift up everyone. It can't not happen this way unless we are people that exist outside of reality itself. Of course, I think it is fine to think being B1 or pro-black (which I do see as the same thing) is only to the benefit of black people.
When used in a negative context, it is evidence of a conscious/unconscious belief that the speaker doesn't believe they are doing/thinking for themselves as much as they think they should. It's projection. "I'm not doing what I believe I should be so I defame the thing I believe I should be doing so I don't have to feel bad about not doing it." Same idea as with racism in that they defame us so they don't have to feel bad about how we are treated. It is why being "woke" is demonized so much in white media.