Anyway. I am not one of the Grammar Police, although a lot of people assume I am because of my day work editing and proofing. That work has actually taught me a great deal about the fluidity and flexibility of language, and has made me reluctant to deal in absolute rules. It's also shown me, many times over, how the Grammar Police make people afraid of their own creativity, so scared of taking chances that they turn out timid, characterless writing—if they write at all.
The GP tend to feel threatened by creativity, and they retreat to the safety of rules. They also tend to be wrong; that's a hazard of absolutes. Sentence fragments? Perfectly okay when used judiciously. Ending a sentence with a preposition? Also okay (the rule was invented in the 19th century by some Victorian idealist who felt English grammar should exactly match that of Latin). Beginning with a conjunction? Fine. Of course one must "learn the rules in order to learn how to break them," as the saying goes, but the overriding conceit of the GP—that there is a Single Correct Way to Write—is dead wrong. There are nearly as many ways as there are writers.
I deal with the legacy of the GP a lot: people who approach professional writing as though primary school left them with subject-specific PTSD. I never use red ink, opting instead for kinder colors of green and purple. I explain why I'm suggesting changes. I don't sneak up behind their desks.
Nevertheless, Weird Al's new song delights me. I agree with most of his points. The definition of "literally" is worth preserving. The distinction between "its" and "it's" is useful and informative, as is that between "irony" and "coincidence." Correct spelling is also useful: it reveals etymology and meaning in unfamiliar words, avoids ambiguity in familiar ones. Punctuation marks are not to be used arbitarily; they too communicate meaning. (I doubt even the most remedial math student would use a plus sign instead of an equals sign on the grounds that "it looks better." But countless people offer that exact justification to use a hyphen, which adds adjacent words into a compound meaning, instead of an em dash, which separates phrases of equal weight.) Usage and spelling matter for the same reason that you would not, on meeting a stranger, clasp his nipple instead of shaking his hand. We are dealing here with human interaction—standards of behavior—and there is much to be said for clarity.
Most of the dissents I've seen have been along the lines of "Language evolves, man, get used to it" (although usually with more spelling errors). Yes! That is exactly the point. Language does evolve—and we all get to have a say in how it evolves. Some philosophers even believe language is the great collective endeavor of the human species. We don't have to sit back and watch as "literally" becomes "possibly literally, but possibly figuratively, but I'm not sure which, because the two differences in meaning register no difference in pronunciation or usage." We get to choose. Not dictate the choice from above, the way the Grammar Police would have it, but create it, with our daily speech and writing. And—as it goes with so many other things—we create it either actively or by indifference. Unless you live a perfectly solitary life, you will contribute.
So, to me, what Weird Al has done is create a very catchy bit of propaganda for the way he would like to see our language evolve. I happen to agree with most of his opinions. But mainly I'm glad that he has opinions at all. I'm excited that people in the public sphere still get passionate about language. I would much rather see it evolve through passion than through indifference.