Pressuring blacks to sound more black, or less white, or whatever, sucks.
However, I don't see anything artificial, phony, or wrong about blacks exhibiting that "switch back and forth" thing. I speak a certain way, at home, that is different from the way I speak when at work. I speak the same way in front of blacks as I do in front of whites, because I'm not into all of that extensive "adjusting for the audience" stuff. However, blacks have a certain way of speaking, when at ease and with each other, that is Their Own Thing, and I don't see a damned thing wrong with it.
The fact that I don't curse a blue streak, when in front of my mother-in-law, does not make me a phony, does it?
So, if blacks have a certain ability to go back and forth between two different dialects, I say good for them.
Speaking on an entirely non-racial basis, the real problem is when we have folks-- from all kinds of backgrounds-- who are so poorly reared and educated that they cannot speak, or write with, proper English, and that's a problem for them, not for the rest of us.
Bottom Line: Blacks pressuring other blacks to not "sound white" is just code for saying, We want you to stay down here with us dumb-asses, and when you use proper English, it makes us feel funny more about ourselves than about you.
Just my cranky opinion.