There is white southern speech that seems to multiply syllables and is difficult to speak unpolitely. It too has a beautiful sound. It lives in Alabama and Southern Mississippi.
But there is also black southern speech that is near unintelligible as English and there is white southern speech that is the same. This speech, black or white sounds worse than uneducated. It is crude. It is vile.
Woah there, Nellie. You seem to be prejudiced against poor whites from the upper South (as opposed to the Coastal Episcopalian dialect of the Deep South). Speech that includes vulgarity and obscenity is indeed crude and vile, but legitimate dialects that a people have inherited from generations cannot be characterized as such (unless they include vulgarity/proganity/obscenity). Would you have everyone in the country sound the same?
And there is Boston. It's hard to tell if that speech sounds uneducated or not. I can't tell if Urdu is uneducated just by hearing it either.
The Boston dialect makes everything sound like the "f"-word. It is very different from the beautiful (and now almost extinct) traditional rural New England accent as typified by Calvin Coolidge, "Titus Moody" (from the old Fred Allen radio show), and Percy Kilbride.
I described the two extremes. I did not refer to the broad middle of southern speech which includes many distinct accents. Southern Louisiana alone has perhaps 5 distinct accents in English, not to mention at least 3 versions of French. I did refer to some of the southern speech as one finds in, say, Southport, Florida. There is not an inordinate amount of cussing but the speech is entirely mumbled and goes along with a manner that resents giving any information to anyone. If you ask a resident what the name of the main street is he will say he doesn't know and you will probably ask for a repeat to try to understand. Southport is an entirely white burglet. There is a sizeable black community over by Caryville, also Florida, that has a nearly identical mumble and attitude. I have also heard the same speech(?) from a pair of Australian youths from Sydney, not what I always thought Australian sounded like.
I know the old New Englend sound you write of. My grandfather had it. I would not characterize it as beautiful, but it is very pleasant and goes with the brevity of speech that seems also to characterize those people. My Grandfather was out of Worcester which now seems to have the worst of the urban Massachessetts sound.