Thanks for starting this! For those not involved in fanfic, it's notable in that it's largely a female community with writing by and for a female audience - and yet there's (IMO) all sorts of internalised misogyny there (hardly surprising I guess given that internalised misogyny is everywhere, and all of us have a hard job throwing it off).
For context, I'm going to post what I put on the kink-shaming thread - apologies, bit of a wall of text. It's about women having rape fantasies, as expressed through fanfiction.
I've been involved in the fanfic scene for some years now (more from a perspective of wanting to write and explore the fictional worlds and characters that grab me perspective rather than indulging kink - I do, however, write vanilla sex scenes on occasion). This has led me to give a lot of thought to why a quite substantial proportion of women genuinely like (however much that liking may be socially conditioned) rape fantasies, given that I cannot get my head round why any woman would.
There's what I call the Libfem analysis: rape fantasies are either a metaphor for overwhelming passion, or they stem from women's internalised suppression of their sexual urges in a society that divides women into "virgins" and "whores" (on this analysis, rape fantasies are the only way "nice girls" can have guilt-free fantasies, because the choice to engage in sex has been taken away from them). I've talked to enough American women shaking off the chains of Evangelical Protestantism and an abstinence only upbringing to know that there's some truth in this as an analysis of the "why", for at least some women. I still don't think it makes it healthy.
Then there's what I think of as the Radfem analysis: rape and sexual assault are ubiquitous in our culture, and pretty much decriminalised (rape convictions are now in the low single digit percentages for reported rapes - and when you consider that most rapes are unreported, this effectively means men can rape with impunity). This leads to a sort of society wide form of Stockholm syndrome: if you can't do anything about the chances of being raped, then (cognitive dissonance as coping strategy) you might as well accept the male gaze and the way male writers/film makers/pornographers eroticise rape. It's like the date rape victim who then has a one or two week attempt at a "relationship" with her rapist (not an uncommon response) in a desperate attempt to normalise what's been done to her and pretend it was just "bad sex" rather than rape. For me, this analysis holds more water (I don't think the two explanations are mutually exclusive - both could explain different parts of what's going on).
(There's also the issue of rape victims using narrative to reframe their experiences and take back control of the narrative.)
What I have no time for is the shitty patriarchal analysis (often dressed up in the pseudo scientific terms of evolutionary psychology/sociobiology) which says "What rape fantasies show us is that rape is natural and even women like it really." And the whole crap about "don't kink shame me" comes dangerously close to this - that enacting any fantasy is okay if you find someone who supposedly consents.
For every woman re-enacting a 50 shades fantasy of rape in the bedroom, there's a man in that bedroom role-playing being a rapist. And for me, the line between role-playing being a rapist and actually being a rapist is so wafer thin it might as well not be there.