Science

Of course there is a proper english. As defined by standard grammatical rules of the English language. A dialect is a variation upon that. I am not saying "black people don't speak proper English". There are plenty of black people who speak proper English, the same as there are plenty of white people who speak proper English and plenty of white people who speak dialects. I am saying that any and all dialects are not formal English, by definition of what the grammatical rules of the language are