Um ... If you ain't black for not being for Joe than you ain't black meaning the Joe got 100% of the black vote. What's so hard to understand about that? Just because your skinfolk doesn't make you kinfolk. Being black is more than just skin color.
"What The African American Saying "All My Skinfolk Ain't My Kinfolk" REALLY Means"
http://pancocojams.blogspot.com/2020/02/what-african-american-saying-all-my_15.html?m=1