As a libertarian-leaning conservative, a practicing Catholic (and I say practicing because I'm pretty sure I'm still not getting it right), and a white cisfemale asexual, I may be too high up on the privilege totem pole to comment on gender matters. Still, I can't help but give in to temptation and share my reactions in re: the current tornado in a teacup.
If Alex MacFarlane wants to use her blog posts at Tor.com to promote works of science fiction that explore gender in non-traditional ways, I -- actually don't have a problem with that. If you feel something is not getting enough attention, it's actually very constructive to attempt to generate buzz on your own. However -- the manner in which MacFarlane broaches the subject in her first column is extraordinarily off-putting for two primary reasons: 1) like many "social justice warriors," she outright refuses to countenance debate when she states that she is "not interested in discussions about the existence of these gender identities"; and 2) she does sound like she's trying to tell people what to write, especially when she declares that she "never again" wants to read sci-fi anthologies or large-cast sci-fi novels in which all the characters fit the gender binary. I don't want to speak for Larry Correia (the principal dissenter in this affair and also a very loud, boisterous man capable of speaking for himself), but I think what really bothered him was MacFarlane's militant, prescriptive tone. You do cross a line when you go from "I want to see [a certain minority] more" to "I don't want to see [the majority] and you're wrong if that's all you're writing."
Due to genetics, prenatal hormones, or other as-yet-undiscovered causes, there are people who are intersex or transgender. But the reason why the male/female binary overwhelmingly dominates fiction is pretty simple: that binary covers the experiences of the vast majority of the human population! People are writing what they know. I can see why that may be difficult for some people to grasp, though, particularly if they've spent their entire lives in academia and/or among the cultural elite. In those sectors, the fetishization of gender and sexual minorities is so firmly entrenched that I really can't fault anyone sunk in such a milieu from concluding that certain things are far more common than they really are. An illustrative story: my co-author, who is currently living in New York City, recently overheard a conversation on the subway between two urban academics in which, I kid you not, one of the woman said, "I'm straight, but I feel like I should start experimenting with women." Why? Because among those of her class, being "queer" is one trendy way you can reinforce your status as a hip, transgressive special snowflake.
The aforementioned fetishization, by the way, is another big reason why, I suspect, people are balking at MacFarlane's mission statement. Do people of her cast of mind see members of gender and sexual minorities as living, breathing people -- or are they merely convenient props for their overall attack on "bourgeois values"? I certainly hope the former is the case, but my experience leads me to suspect the latter. Another illustrative story: In the past week, a sadly typical text post made the rounds on Tumblr (a space dominated by feminists and other leftists of MacFarlane's ilk) in which the author stated that heterosexual men were obviously "weak and pathetic" if they couldn't control their reaction to scantily clad women given that gay women have no trouble in similar situations. In other words, said Tumblr user seemed to be of the opinion that lesbians were utterly incapable of being inappropriate. The very idea is ridiculous -- unless you honestly see "queer" individuals as abstract saints instead of concrete human beings. And you know what? I wince too when I imagine people with this worldview attempting to write stories featuring non-binary or gay protagonists. Do you honestly think they will create fully realized characters? Will they have room for an orthodox Catholic intersex pansexual who is remaining celibate in obedience to the Faith? Will they have room for a transfemale who drives pick-up trucks, hunts, and votes Republican because she's a proud capitalist? Will they have room for a lesbian monarchist? (I have a friend who is one! They do exist!) Or will they produce nothing but grey, mushy, politically correct pablum? Other people have made this point, but it bears repeating: If all you have to hang your story on is a vague desire to "smash the gender binary," your work will only appeal to people who think just like you do -- a niche market at best. You have to offer more - like, for example, a compelling plot and interesting, recognizably human characters - to reach the general public.
The ticky-box approach to writing science fiction is, ultimately, a shallow affair. Race, gender, and sexual orientation do influence a person in significant ways, but they are hardly the only facets of personality. Focusing on these things to the exclusion of all else is, when you get right down to it, deeply inhuman -- and also leads to division and strife, not genuine tolerance. Think about the lurking assumption that undergirds the entire "representation" crusade: If a character doesn't look like you or have sex like you, you can't possibly sympathize with or be inspired by that character. Really? Because in my life as a science fiction fan, I have had no trouble falling in love with characters who didn't share my race, gender identity, or sexual orientation so long as they were well written. Remember, I was raised in part by Robert A. Heinlein. The juveniles he serialized in Boy's Life featured male protagonists -- but that didn't bother me one iota. As a little girl, I never once caught myself saying, "Gee, I could get into this book more if the main character were a girl like me." Kids just don't think that way -- until adults with axes to grind teach them to.
TL;DR: Theoretically, I don't see anything wrong with promoting works that go beyond the gender binary -- but the overall context in which MacFarlane's post appeared and the tone she employed prompts, in my opinion, justifiable suspicion that this is yet another project to force a very narrow worldview on the science fiction community in lieu of penning strong stories with universal appeal. And yes, Larry Correia is right -- if successful, such a project will further hamper the genre's commercial prospects and alienate potential readers.