I don't agree with every point Wolverton makes, and I do agree with you that he overstates his case in some respects. But I think that his explanation of how the current standard of what constitutes "literary" came into being, and how arbitrary and unfair and even silly that standard really is, makes the essay worth reading.

I didn't get the impression he was saying "all genre fiction is great and all literary fiction is terrible", either, or even that he was deliberately choosing the worst examples of literary fiction. He chose a work of literary fiction (Il Postino) which was widely praised by people who value literary fiction, and the "Manhattan Angst" stories were but one extreme example among several less extreme.

So yes, by no means a perfect essay -- but I felt that its sound and well-made points considerably outnumbered the exaggerated or spurious ones.