'Correct grammar': What are the rules of this game?

I assume that William Safire, secure in his willful ignorance of the most basic notions about how language works (structurally, cognitively, socially, historically), at least has a clear purpose in what he does: He’s an unabashed elitist, trying to promote what sociolinguists think of as standard language ideology and enforce a certain set of norms. (Rosina Lippi-Green’s excellent English with an Accent is a good place to read up on this.) And he sees it as within his personal purview to declare what’s good and bad, right and wrong. Given how often he does this without checking facts or standard reference sources, we can usually smell the rank Air of Superiority oozing from his pores. (That his constant, simple blunders go uncorrected, unregulated and unpunished by the New York Times has damaged or destroyed the paper’s reputation for some of us.)

A very different case of norm enforcement is Barbara Wallraff’s Word Court, a column and a website that’s decidedly less pretentious than anything Safire would have his name on. Her shtick is that she’s a judge of language disputes, an arbiter of correct grammar. This week’s column in the local paper here runs under the headline: “Better not use phrase ‘we best’”. It’s about a parent bothered by their three-year-old coming home using the construction ‘we best do X’. She asserts that ‘you better’ or ‘you best’ are wrong: “you need ‘had’ – or ‘‘d’, as in ‘I’d’ – for the phrase to be grammatically correct.” Says who?

This form is listed in the standard sources one would consult for such purposes: I checked Merriam-Webster’s 11th Collegiate, which dates it to 1914 and gives the example sentence “you best listen”, calling it a ‘verbal auxiliary’. OED On-line takes it back to 1831 and regards it as colloquial (and surely colloquial English is fine for a three-year-old; the kid can learn a few things before she writes her dissertation) – originally an Americanism. Greenbaum’s 1996 Oxford English Grammar, p. 583, treats it as one of the set of auxiliaries and semi-auxiliaries that don’t inflect (like ought to, must, etc.). The Merriam-Webster's Dictionary of English Usage treats 'better' rather than 'best' and quotes Copperud's American Usage from 1970 already as arguing that the "consensus is that it is not open to serious criticism".

I’m no legal scholar, but isn’t a judge obligated to uphold the law, not create it? Even if we buy into standard language ideology, what’s her basis for this? Are these people so extreme that sources like the ones cited here are regarded as contributing to the downfall of the language? This needs to be overturned on appeal and the judge deserves a reprimand, if not impeachment.