This maybe goes too far. I think in general we should call people what they want to be called (Wallace implicitly recognizes this when he talks about PC English as a matter of politeness), but he's right that changing language does not change reality, and excessive focus on language means turning one's back on reality. Which is not good.
I'm not sure that any reference to either Plato or Derrida is really helpful here, but this otherwise looks like a nice disposal of a badly thought out position.
This, on the other hand, is poor. Arguing from universal acceptance is weak, a is true only if we take 'interpret' in a special sense (as 'understanding', roughly), and b is only true if we take 'ideology' in a special sense (as 'way of thinking', perhaps). The main idea is that all language is political. This, it seems to me, is both true and false. It's true in the sense that language is a human product, a social product, and reflects various social relations and practices, past and present. There is obviously something political about this. Perhaps social relations are just by definition political. But the claim is false in suggesting that all attention to language is political and therefore important. Wallace's own insights on political correctness show this.
(SWE = Standard Written English.) I think this is true, and why we owe it to our students to teach them SWE. It is easily understandable why many people would regard this truth as a bad thing, but that doesn't justify pretending that it isn't true. And it is understandable that many people would not want to teach SWE, because it's tedious or seemingly unchallenging intellectually, but that isn't a good reason not to do it. Matt Reed, in talking about college composition courses, writes:
For the sake of argument, let’s assume that most grammar instruction has been delegated to the K-12 system -- elementary schools were once called “grammar schools” for a reason -- with developmental courses available for the many students who still need to work on that. 101 [i.e. an introductory course on composition] is intended to address college-level skills.I don't think the assumption he wants to make is reasonable at all. The reason we have these courses is because so many students do not know SWE well enough. Wallace again:
Reed's assumption "for the sake of argument" is contrary to a well-known fact. That's a bad kind of assumption to make for any reason. Not that we should necessarily have classes explicitly in SWE. They might not be needed at every college. And Wallace notes that such courses are said to have been proven ineffective. He suggests teaching them in a different way. Whether that would work remains to be shown. I have never had a class explicitly on English grammar or style, and I write as well as I want my students to. So direct instruction in how to write English might not be necessary. Perhaps all we need is the teaching of writing across the curriculum, and one or two courses in which students read excellent writing and are required to write in correct SWE about it. But Wallace is right to point out the practical (however regrettable or immoral) need for students to learn SWE and the fact that they aren't generally learning it now.
In short, there is a lot of good stuff in Wallace's essay. It's a long essay, packed with footnotes (which is, and are, not always as funny as I take it they are meant to be, but hopefully you'll react differently), but well worth the time it takes to read it.