I believe that Black people in American societies have been and to a large degree still are measured by idealized White standards of speech

English as a language is subject to standards of spelling and grammar that are not white or black, but originate in an agreed set of rules as expressed in the Oxford English Dictionary and elsewhere. The ability to communicate in English in an articulate fashion is subject to these same standards, and is the product of education, awareness, and intelligence. Those who consistently display an inability to communicate clearly and articulately are considered, in my opinion, ignorant and uneducated, and sometimes stupid, whether black, white, rich, poor, and regardless of their background. For any one in an English-speaking culture who wishes to be clearly understood and who wishes to succeed in any endeavor, a mastery of the language has always been a strong tool to that end. Obama understands this, I believe.