In response...

I would like to quote a bit of Ellisonia back at you.

"What I am suggesting is that when you go back you do not find a pure stream; after all, Louis Armstrong, growing up in New Orleans, was taught to play a rather strict type of military music before he found his jazz and blues voice.  Talk about cultural pluralism!  It's the air we breathe; it's the ground we stand on.  It's what we have to come to grips with as we discover who we are and what we want to add to the ongoing definition of the American experience. ...It is very difficult in this country to find a pure situation." -RE on Alain Locke in The Collected Essays of R.E.

I think Mr. Ellison might respond to your post with something like this in his own blog. He might remind us that while we are all human, there seems to be a certain significance in the cultures through which we are borne and that for Americans, and especially Black Americans, this is a cause for celebration.  It should go without saying that we are all fundamentally human, and while this has not always been the case, we should consider it our job to elevate this discourse and claim the complexity and difference between us. Mr. Ellison might even playfully ask why we insist on speaking on the, ahem, "lower frequencies," when we could bring to light the richness of this cultural pluralism. (10 points for the lower frequencies joke)

My sense is that while there is certainly something unifying about Americanness, and Humanity in the broadest sense, some would resist throwing Race out with the bath water. 

Here's one more for the road:

"Speaking of language, whenever anyone tells you that you're outside the framework of American culture, and when they deflect you into something called 'black English,' remember that the American version of the English language was born in rebellion against proper English usage, and that the music of the African voice and the imagery coming from the people who lived close to the soil and under the conditions of slavery added greatly to that language."