This seems to make the ludicrous argument that because the mistakes are consistent they are not mistakes.
What is any dialect or derived language but a set of consistent mistakes with respect to the ancestor language? A dialect that lacks prestige is no less a dialect for it — that was one of the points of the article.
However to accept it as a legitimate dialect is another thing. If your child spoke that way you would constantly correct them, for their own good. It'd be much better for all involved to redefine "dialect" to not include something that devolved from another language via mistakes made by dumb rednecks who can't understand the concept of a double negative.
If we call that a dialect, then the very word "dialect" is broken.