All of you have been quite patient — at least those who keep returning — as I've tried to articulate a reasonable understanding of responsible editing. The extremes are easy to work out: A responsible editor doesn't attempt to supplant the writer; neither does a responsible editor become enmeshed in fetishes.
One help at clarifying the basic principles comes from the first chapter of the late Dwight Bolinger's Language — The Loaded Weapon: The Use and Abuse of Language Today:
We are attempting, he suggests, "to save the English-speaking world from mistakes in grammar and individual word choice, speech or writing that fails through ineptness to communicate its intent, or the kinds of language (or non-language) designed, like the Barnum and Bailey sign This Way to the Egress, to lead the circus-goers out of the tent when they would rather look around some more."
He adds: "Only the last two questions have an ethical side, and the shaman* speaks almost exclusively of the first two (sometimes of the third, but usually in terms of the second), yet regards his judgments as ethical ones."
Hardly anyone could quarrel, I think with the main goals, to correct errors, reduce confusion and avoid dishonesty —though many editors enforce "rules" that are merely idiosyncratic preferences, misguided principles or fossil usages. The larger problem may lie in confusing social distinctions with ethical distinctions, snobbery with morality. Splitting an infinitive or using hopefully to mean it is hoped that may not be to your taste, but neither is wrong, and neither is an indication that barbarian hordes are at the point of breaching the walls. You may wince, as I do, at talk of growing the business, but it is not an error so much as it is a slogan ritually chanted.
Professor Bolinger's book, nearly 30 years old but which I am just reading for the first time, sets out to establish a common ground for students of the language, both shamans and linguists, an enterprise of which I see occasional evidence at Language Log. Sadly [please note adverb of emotion, like hopefully, used as a sentence adverb], considerable distrust and hostility survive, as evidenced in this comment to a previous post mentioning the linguists: "It's rather sad to see you brown-nosing those boors at Language Log. I thought, based upon your previous posts, that you had a backbone." (I have my own suspicions about the origins of the hostility between journalists and linguists. **) Spine or no spine, I suspect that we might have more sensible editing if more copy editors spent some time with the Bolinger book.
English is evolving, as it always has, not decaying. To be an effective editor means to be able to make thoughtful discriminations between different levels and dialects of the language, as appropriate to the subject and the occasion. Linguistics contributes to the ability to make those distinctions, as was suggested many years ago by that self-taught journalist and scholar, H.L. Mencken, in The American Language:
"The error of ... viewers with alarm is in assuming that there is enough magic in pedagogy to teach 'correct' English to the plain people. There is, in fact, too little; even the fearsome abracadabra of Teachers College, Columbia, will never suffice for the purpose. The plain people will always make their own language, and the best that grammarians can do is to follow after it, haltingly, and often without much insight. Their lives would be more comfortable if they ceased to repine over it, and instead gave it some hard study. It is very amusing, and not a little instructive."
* Shaman is Professor Bolinger's term for self-appointed language experts, like your humble You Don't Sayer, who have some useful advice mingled with shibboleth and superstition — the people Steven Pinker calls "language mavens" in The Language Instinct.
** Not that I want to fall into some giddy excess of indulgence in footnotes in the David Foster Wallace manner, but I have to disclose a painful truth without shouting it. Many journalists, like most college graduates of the past 40 years (the period of my direct experience) are not particularly well educated. Before you leap screaming from your chair, keep in mind that I have 13 years' worth of copy desk applicant tests to draw from in support of this contention, not to mention the things I see in the daily flow of copy. It's a serious mistake to dismiss tout court the work of people who have given serious study to the workings of the language.