My favorite part of the second chapter of Ursula K. Le Guin’s Steering the Craft is her “opinion piece” (i.e. rant) on “Grammatical Correctness.” Here’s just a bit of it:
I detest the self-righteous tones of those who sneer at other people’s speech, and I distrust their motives. But I have to walk a razor’s edge here in this book, because the fact is that “incorrect” usage, in written prose, unless part of a conscious, consistent dialect voice, is disastrous. It can invalidate a whole piece. How can a reader trust a writer who seems to be ignorant of the medium she works in?