Tell a story about each one.
Suggesting that speaking proper English is trying to "be white" is like telling black people they should voluntarily ride on the back of the bus in order to honor their heritage.
When a person grows up on a backcountry Southern farm, gets good grades in high-school, goes on to college, and starts a successful business, few chastise that person for speaking standard American English. Few say that they are denying their heritage by not continuing to talk in the style of the independent paragraph above. Few say they are "trying to be urban mid-western" or "trying to be urban northern Californian", (which are the accents which most America's think of as a "neutral" American accent, even among people who have a different accent themselves.)
Because, no matter what initial thought flashes through the sub-conscious of whatever cop / employer / landlord, all it takes is a couple seconds of me opening my mouth and speaking to correct whatever preconceptions they may have had about me as an individual.
I have linked to this video before, after the uproar over Oscar Grant's shooting, but it is still a lesson a lot of people need to learn:
There are two factors that should be kept in mind when looking at statistics around race.