He's absolutely lecturing. The title of the piece is a command: "CONSIDER the lobster." There is no room for the notion that everyone reading had already considered the lobster and had come to their own conclusions.

More than that, it's a piece on a lobster festival - an archetypal slice of americana in which only four of the article's 32 paragraphs are even glancingly about the festival itself.

If someone turned in an 8,000 word video game review in which barely a thousand words were about the video game but seven thousand were about the ethics of free-to-play, no one would consider it a good article -

...unless it was written by David Foster Wallace.

Finally, there's this:

Given this article’s venue and my own lack of culinary sophistication, I’m curious about whether the reader can identify with any of these reactions and acknowledgments and discomforts. I am also concerned not to come off as shrill or preachy when what I really am is confused. Given the (possible) moral status and (very possible) physical suffering of the animals involved, what ethical convictions do gourmets evolve that allow them not just to eat but to savor and enjoy flesh-based viands (since of course refined enjoyment, rather than just ingestion, is the whole point of gastronomy)? And for those gourmets who’ll have no truck with convictions or rationales and who regard stuff like the previous paragraph as just so much pointless navel-gazing, what makes it feel okay, inside, to dismiss the whole issue out of hand? That is, is their refusal to think about any of this the product of actual thought, or is it just that they don’t want to think about it? Do they ever think about their reluctance to think about it? After all, isn’t being extra aware and attentive and thoughtful about one’s food and its overall context part of what distinguishes a real gourmet? Or is all the gourmet’s extra attention and sensibility just supposed to be aesthetic, gustatory?

This is a magazine article by a freelance contributor that finishes with SIX questions. How, exactly, is Mr. Wallace supposed to get his answers? How can they therefore be anything other than rhetorical? And how is finishing an 8,000 word screed with rhetorical questions anything but condescending and trite?

People tell me I oughtta read David Foster Wallace about twice a year. They have since he was alive. And every now and then I get forgetful and think "You know, I really oughtta read The Infinite Jest. People dig that." And then whoever I'm talking to says "You totally should! DFW is, like, SOOOOOO amazing!"

And then I remember that David Foster Wallace wrote that shite lobster piece in Gourmet.