Fandom on the internet in general is a pretty fantastic place, but particularly when it comes to sexuality. Kink, taboos, paraphilias, and pretty much anything you can think of get addressed in fandom; written about, debated, discussed. If you think you're the most sexually liberal-minded person out there, you're probably wrong. It's never-ending. Sexualities of any and all sorts get treated with respect, or at the very least, curiosity and genuine interest.
Fandom is a kinky place; I don't think of myself as easily shocked (anymore), but occasionally someone will request a fic that has even me turning pale and looking for the nearest Disney film to recuperate. I've discovered squicks (don't google that) I never knew I had, but I've also realized that I'm comfortable with the idea of much more than I would have been. Kink and fandom are extremely comfortable with one another.
Which is, I suppose, why the one sexual orientation I still see treated with disregard and outright denial is asexuality.
A lot of fandom doesn't understand why some people think Character A is asexual, because that doesn't exist. The character is repressed, or celibate, or damaged, or busy, or just has never had the opportunity. Authors who write Character A as asexual are fooling themselves, falling for the very delusion that the character is under. At the very best, asexuality is a choice, one that Character A makes for personal, religious, or whatever reasons, and which can be un-made when they realize just how darned attractive Character B is.
This is one of the rare times when fandom attitudes overlap with life. Asexual people are told, constantly, that they cannot, and do not, exist; that their orientation is not valid; that they must have been abused, or traumatized, or hurt in some way; that they have a hormone imbalance; that there is some reason why they are like this; that they're not normal. Asexual people are told that if they just give sex a try, they'll like it! They're told that asexual means "bisexual without experience". Sex is "only human", and "natural", and asexuals are not just denying themselves, but supporting the anti-sex patriarchal whatever. Finding this attitude so condemningly — and, yes, condescendingly — in fandom, a self-professed safe space, is unbelievably frustrating.
You'd be hard-pressed to find a place where sex is stigmatized less than in fandom. While society still persists in slut-shaming and any horrifying number of attacks against sex, fandom is, in general, a place that celebrates sex. All kinds of it. Perhaps that's why fandom sees asexuality as something to be derided and ignored — it's no fun. It's not titillating. To put it crudely, you can't get off on it.
Which is why I'm so, so grateful for Sherlock. BBC's modern retelling of Sherlock Holmes has Holmes as decidedly asexual, professing outright to have no interest in any sort of relationship — hetero, homo, or otherwise. This is in keeping with Doyle's version, and I was thrilled to see it.
Of course fandom is rife with Sherlock/Watson slash stories anyway, and at the very beginning I read a horrifying fan-article where the author basically derided anyone "deluded" enough to write Sherlock as asexual, but the attitude is changing. Asexuality visiblity is beginning to happen. Fandom is, slowly, beginning to realize that asexuality exists, and that asexual people can be just as interesting as sexual ones.
Then again, Sherlock is a "high-functioning sociopath", which gives people a "reason" for his asexuality, so we've still a way yet. Most characters in fandom who do register as asexual are otherwise strange. If you want to claim that a character is asexual, be prepared for people to leap on you with reasons why you're wrong. (Case in point: Jughead Jones and Velma Dinkley are, in my mind, firmly asexual. But Velma is a lesbian icon for some reason, despite showing no interest or tendency toward either sex, and people don't want that taken away from them.)
My point here is that if you are a person in fandom whose initial response to asexuality is to scoff and denounce its existence — and, even worse, to argue with an asexual person that they're not really that way — please stop. Remember that fandom is a place that gives voice to people who have sex with anyone — and in any manner — they so desire, and it should also give voice to those who don't.
[Note: maybe later I'll make a post on asexualty vs. aromanticism. Sherlock, for example, is asexual, but whether he's truly aromantic is up for debate. We'll see.]