From a linguistic standpoint, all languages and dialects are equally valid. Some are better at doing certain things -- more vocabulary, more concise encoding -- but they all have strengths and weaknesses. "Standard" just means that a dialect is spoken/written by people who are more numerous, popular, or powerful. It's not better. It's merely considered more important.
As a writer, I think a lot about word choice. So I try to pay attention to subculture and dialect, language and register. I probably don't get it all perfect, but at least I'm making an effort to show the great diversity of communication. When I write black characters talking in dialect, it's not because I think less of them, but because I feel they have a right to say what they damn please and not edit things for someone else's gratification. It's just as good as anyone else's dialect, it has rules and meaning and nuance. Because if your characters look different but all talk the same, you haven't done a whole lot for diversity, because there's a whole branch of racism that puts up with people's skin tone if they act white. Fuck it. Be yourselves, my mad beautiful people. If you done said it, I'll write it down.