that denying whiteness in one's comportment has much to do with one's possible mixed heritage within the Black community. I think that most American Black people/African-Americans can claim white ancestory somewhere in their bloodline.
In fact, being of "mixed" blood was never considered a drawback that I can recall. Black Folks, for the most part, have not had a problem with this. As proof, I offer that characteristics such as "good Hair", light eyes or fair skin actually have connotated positive attributes of beauty in the Black community.
"Acting White" is a different issue althogether, in my view. It has more to do with terms translated by some in the Black community as acting "uppity" or appearing "snobbish". There is a definite discussion going on in the Black community about this particular issue, which is complex enough in itself.
There is a very interesting recent thread dealing directly with this issue here.....
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=258&topic_id=288&mesg_id=288Read it.....as it will provide some insight and the different takes that this one issue generates.