Fish on Writing

Stanley Fish:

It may be true that the standard language is an instrument of power and a device for protecting the status quo, but that very truth is a reason for teaching it to students who are being prepared for entry into the world as it now is rather than the world as it might be in some utopian imagination — all dialects equal, all habit of speech and writing equally rewarded.

The entire series of posts (I,II, III) is worth a read.