Why do so many Golden Age SF authors look down on Literature? Heinlein is the most obvious example, in that he occasionally used the term "Literature" as an insult in his stories. Ayn Rand looked down on it, too, which is a little ironic since she's actually considered Literature these days. So why the deliberately lowbrow stance towards art?
First of all, literary critics are, by their definition, critical. It's their job to say "This is a turd" or "Say, this is pretty good!" Secondly, early SF like the main sequence HG Wells stuff was very well regarded. Much of it is actually considered Literature in some circles. (Albeit low-grade entry level stuff) I can cite a bunch of SF works that are considered Literature: Gravity's Rainbow, Ada, Slaughterhouse 5, Fahrenheit 451, etc.
There *IS* definitely a rivalry between genre and Literature, but I think that stems from two different sources:
1) *Most* SF writers, particularly the early ones, couldn't write for sour apples. I mean, seriously, much as I love Smith's "Venus Equilateral" Stories - I'm re-reading 'em now - the guy thinks nothing of stopping the action to go on for pages at a time about how to tune a cathode so as to minimize the erosion of the anode under current. And Smith had a real gift for dialog, which puts him waaaaaaaay above most of his peers. Or take Clarke and Asimov and Heinlein: Clarke never wrapped his brain around the need for a plot, and as Asimov was about as dry as an instruction manual for eating crackers. Heinlein was unquestionably the best in his field for the day, but outside of his field? Come on! 'Tunnel in the Sky,' 'Lolita,' and 'The Return of the King' all came out in 1955. I can cite scores of better writers from his period who *weren't* in the genre. Being a big fish in a small pond doesn't change the fact that there are bigger fish in the sea beyond.
So it's fitting that critics should be critical of this stuff. And it's entirely fitting that SF authors - particularly the early, inartistic ones - should feel looked down upon and oppressed for it, and resentful. I mean, authors of Cowboy novels and Detective fiction feel the same way about Literary criticism.
2) The bigger reason, I think, is a right brain/left brain thing. Again: Take Heinlein, Asimov, and Clarke: All three were engineers. All three were very logical, very rational. Heinlein had no use, whatsoever, for any aspect of society or culture that didn't conform to his rational view of the world. Antithetical to religion, intolerant of politics, dismissive of capitalism as written, and nearly all of his books are written from the point of view that says "Everyone is an idiot except for me." Clarke, likewise, displays a complete lack of understanding of every aspect of normal human life ("There are more television programs now than a person could watch, even if he did nothing but watch all day long!" from Childhood's End). Asimov is an exception, but we clearly know which side of the Spock divide he's on, right?
This isn't a criticism, it's just the way they saw the world, and if they were a little Aspergery, well, I certainly don't fault that. However they were writing pulp of a technobabbly nature, which tended to appeal to other people of an aspergery nature, so early SF tended to be of an very left brained.
Literature, on the other hand, tends to be more intuitive, more artistic, more emotional, more right brained. So conflict is probably unavoidable. "Ew! That stuff is for girls! My mom would like that! Ew!"
It's worth noting that most of the authors who tended to write nontechnical stuff back in the day *also* tended to get looked down upon by the more stalwart fans of Asimov, Clarke, Heinlein, etc. Bradbury, for instance, Dick's early stuff. And as the New Wave really got going in SF, most of the old guard technical writers utterly hated that, and were highly critical of it. So that would seem to bear out my theory.
Conversely, because SF tended to have comparatively poor writing in the early days, with little or no characterization, minimalistic plots, no subtext or subtlety, and tended towards the technical, it was perceived by high-falutin' critics as being the kind of embarrassing stuff that was only read by adolescent compulsive masturbaters, which is why they go to such great lengths to this very day to pretend the SF they like isn't really SF.