the three classes of language being good, bad and... different!

This is an excellent proposal. Good language is good because it works. Bad language is bad because it doesn't. People who are good at good language tend to lump different language in with the bad, because it doesn't work for them. If it works for others (e.g. the homies in the hood) then it is not so much bad as just different.

How do you suppose the French think of the patois spoken in the Channel Islands?

How do you suppose speakers of Icelandic and Norwegian think of that language spoken in the Faroe Islands?

What does a Continental Portuguese speaker think when she hears someone from Rio Grande do Sul speaking the Gaśchan dialect of Brazillian Portuguese (in a way that is more understandable to some Argentinians)?

I am not hanging up my prescriptivist spurs hereby, but am admitting that, in addition to good English and bad English, there is also different English.