[W]riters of genre-fiction have not done themselves any great favors by reactively ignoring the tools of the so-called enemy, which most critically include the entire history of theory, or the third stage in a generalized history of intellectual thought that began with ontology, metamorphosed into epistemology, and has most recently (post-Saussure) settled upon linguistics. Let me say that again but more clearly. Genre fiction writers interested in creating a theory of what they do and how they do it are missing the boat by avoiding theory and the entire history of academic thinking around the subject. For a writer to ignore theory is akin to a scientist ignoring Newton, or Gould, or Hawking. My secondary point is thus that until more (for some are already quite well-versed, and the trend is growing) writers stop making excuses to avoid theory, which is not easy stuff whether you're "initiated" or not, it will remain unintegrated, cordoned off, separated by the same sort of elitist ignorance that created the problem of genres in the first place.While perhaps having more SF writers who are familiar with both modern and classical literary theory writing critical essays would be helpful, the idea that mainstream writers have imbibed theory and therefore written well is absurd and completely unsupported by history. (Trent at s1ngularity offers some thoughts on all this.)
The fact is, most fiction writers, poets, and playwrights have gone out of their way to avoid theory. Finding ones who haven't, and who have achieved success within the academic literary world (that is, their works are included on numerous syllabi), is difficult. Every now and then there's someone like Susan Sontag, but the general agreement is that her nonfiction is vastly superior to her fiction, particularly her early, theory-influenced fiction. William Gass knows some theory, since he's a professor of philosophy, and some of his work may have been influenced by it, but my sense of his writing is that he gets more influence from other writers he admires, such as Rilke, Malcolm Lowry, and John Barth. A few writers on the fringes of the avant-garde have made a lot of theory, but really the only fiction writer I can think of to have achieved some prominence while also deliberately attempting to write with critical theory in mind is Samuel Delany, who receives no mention in Peckham's rant, though he'd be an obvious choice of a writer to hold up as a role model.
Theory can be fascinating and can help us read in different ways, but the fact is, 99% of the writers out there couldn't care less about it. From Aristotle on, theory has been written to show what writings have done, to point out ways of interpreting and evaluating, but it's about as useful to writers as real estate listings are to architects.