While you are right on several accounts, there is no central leadership or unified body on what decides "black" culture, you are incorrect in stating that there is no black culture. There is, and it is the result of the African-American experience since the arrival of "20 and odd" Africans in 1619 Virginia. Not every African American ascribes to every part of the culture, just as every American doesn't have a barbeque war like North Carolina does.
As well, no one said the culture exists in a vacuum, it has influence from the works of Native Americans, Spaniards, English, French, et cetera. However, that doesn't mean it isn't something unique to African-Americans, be it the music, food, dialect, or otherwise.
I have no anger with you, however I hope you realize that there is a unique culture to be found.