My dearest and most esteemed Wombles:
For the record, I agree almost entirely with your immediately preceeding post. However, as is my wont, I have a few gratuitous comments.
1. OK, OK, grammar is descriptive, not prescriptive. Language is dynamic, not static. Language is whatever bits of sound and scribbles we use to communicate with each other. But...
At any single point in time, don't we have some collective idea of what is and isn't correct, accepted language? When I say that something is not grammatically correct, you know what I mean. We always have some loose concensus of what correct grammar is. This may be a fluid concensus, but we do collectively set parameters on what is and what is not an acceptible, "correct" way to use our shared language.
Given that, isn't it acceptible to say that a given statement isn't grammatical? "Pwned" may become a perfectly cromulent English word in a few more years, but as yet it has not reached full acceptance. Therefore it is incorrect in some sense to use it. Also relevant is the nature and degree of the incogruity with the accepted rules. Blatant violations of subject-verb agreement or tense formation seem less likely to become acceptible through evolutionary change than do neologisms, back-formations and mispronunciations.
2. Yes, language is always changing and evolving. But can't we take a snapshot and have at least a decent idea of what is acceptable right now? And if so, can't we learn something about the speaker from his usage? I think what we collectively disdain in our "Grammar Cop" posts is willful ignorance. Empirically, I've found that people who are willfully ignorant about our language are usually willfully ignorant about everything else. The structure of language is how we arrange our thoughts, emotions and desires for presentation to the rest of the world. An inability or unwillingness to do so in a coherent (if not artful) manner speaks for itself.
3. I have only a couple gratuitous comments rather than a few. Please forgive me.