It doesn't matter where you come from, what accent you have, what dialect you speak or whether you use slang words or colloquialisms. It's more about illiteracy, impoliteness, ignorance and inappropriate language for the situation at hand. I'm a born East Londonder with what is generally considered to be a Cockney accent, but it doesn't make me any less valuable as a human being. I know how to use language appropriately according to the circumstances I find myself in. I wouldn't write as I speak and I wouldn't speak in a formal situation as I would talk to my close friends and family. Schools should always teach the proper use of the English language regardless of local idiosyncrasies. The language will still evolve, just as it always has done.