Proshippers do not "love" these things. Rather, we're committed to defending the right of people to write about them - even in ways we might personally find disgusting or upsetting - because we understand that engaging with something in fiction is not predicated on defending or desiring it in real life. Even if someone is aroused by something in fiction, it doesn't logically follow that they're aroused by the same thing in real life, because context - the question of how, when, why and with whom - is foundational to both desire and consent. Meaning: it is possible - and, indeed, extremely normal - to enjoy something only as a fantasy: to be compelled, aroused by or interested in it only because it's fictional, in much the same way that we might be compelled, aroused by or interested in all manner of ideas or activities only under specific conditions.
For instance: I enjoy cake! But if someone handed me a piece of filthy, rotting cake they found on the floor, I would not want to eat it, because the context of the cake matters to my willingness to consume it. Similarly, I enjoy murder mysteries! But if someone in my life was brutally killed by an unknown assailant, I would be devastated, not entertained. And this latter example is particularly important, because our consumption of fiction is at all times informed by our awareness of the fact that the characters don't exist. No matter what befalls them on page, stage or screen, no real person has been harmed, which allows us to react to the content differently than if we were seeing the same events unfold in person, or in a live recording.
Now: it's true that, just as fiction is influenced by reality, so too can reality be influenced by fiction, both on the individual level and at scale. Fictional characters might not exist, but their stories still meaningfully impact real human beings, both positively and negatively. But this impact doesn't work on anything even vaguely resembling a universal, one-to-one basis, such that X story is guaranteed to cause Y effect, or that X topic is only ever explored for Y reason - and this is just as true for dark, unsettling and taboo topics as for anything else.
Which is why it's important to understand that, particularly when it comes to sex and desire, human beings are complex. At the most basic level of arousal, our bodies and brains are frequently in conflict. From teenagers dealing with unwanted erections to seniors mourning their loss of libido, none of us has perfect control over when and how we get turned on - and this extends to situations involving rape and assault. It is common, for instance, for rape victims to experience some level of arousal in response to their assault, because our bodies and minds do not exist in a state of perfect sync. Many victims experience deep shame as a result of this, thinking that, because they got hard or wet or came, they must've secretly wanted it - a trauma that's intensified if their assailant makes the same claim. Victims, too, can have complex relationships to their assailants, particularly if they were abused by family members or as children; can sometimes take years or decades to understand that they were harmed at all.
Regardless of whether we've been victimised ourselves, are proximal to someone else's trauma or are simply impacted by living in a world where such things can happen, fiction is the safest possible way to explore these ideas. But precisely because people are so different - precisely because our reactions to the same event or idea can vary so wildly - these stories will not always look the same. What disgusts or triggers one person might be healing to another, and that's not determined by how eroticized the content is or isn't. Sexual trauma responses can encompass opposite extremes: where one rape victim might be utterly repulsed by rape content and need to avoid it for their healing, another victim will feel compelled to seek or create it in order to achieve the same ends, and neither of them is wrong.
I have, for instance, known victims to write their own assaults into fiction. Sometimes these accounts are eroticized as a way of regaining control over a situation in which they had none. Perhaps the writer wants to accurately depict the confusion they felt at being aroused while being assaulted; or, conversely, perhaps their lack of arousal at the time increased the level of physical pain they experienced, and they want to write something which shows that, even if they had been aroused, it would still have been rape. Or on yet a third hand, perhaps they weren't sure if a given experience was rape or not, and want to try and make sense of it. Perhaps they want to try and imagine their assailant's perspective, to better comprehend what happened to them and why. This might mean a complicated, nuanced depiction that sways between awareness of the crime and minimization of it; it might also involve painting them as a flat-out villain, or as someone who believed they were acting only out of love. All of these things are possible! But no matter how much some or all of these portrayals might disgust you, the casual reader, you will not be able to tell, just by looking, who has "really" been assaulted, and who is exploring these topics for other reasons.
Because of course, not all people who write about abuse have experienced it themselves; nor should this be a requirement. Sometimes, we write about dark things, not to achieve catharsis in relation to a personal experience, but to conquer our fear of it happening to us, or perhaps even just to get an adrenaline rush - as is, for instance, extremely common with fans of horror content. Our brains produce a variety of fun chemicals in response to various stimuli, and we don't generally get to choose which ones we find the most engaging. Some people are horror junkies from childhood, seeking out scary stories from the moment they're old enough to ask for them, while others remain terrified of something as mild as cartoon comedy horror well into old age. There's no morality associated with this; it just is - and that all comes back, once again, to the fact that we understand fiction as a separate thing to reality. No matter how horrific the thing depicted, our enjoyment (of whatever kind) is predicated on knowing that no actual human beings being harmed, even if the bad in the story - an axe murder, a war, a rape - is something that really does happen.
And returning again to matters of sex, regardless of whether they rise to the level of a kink or fetish, all sexual proclivities are ultimately products of native inclination, life experience, trauma, and/or the overlap of all three, while a specific fantasy might be either literal, metaphoric or a mix of both. A literal fantasy, for instance, might be: what if my hot boss fucked me over his desk at work, because he's hot and I want to sleep with him. A metaphoric version of the same fantasy might be: what if I was so insanely desirable that my boss fucked me despite his being married and straight and me being a man.
To take another example, and one which has been studied extensively by psychologists, literary historians and academics alike, rape fantasies are commonplace, not because the vast majority of people are rape apologists, but because, at the level of metaphor, they allow the possibility of sex without having to take ownership of one's own desires, which is of particular value if, say, you've been taught that wanting sex makes you slutty and wrong and gross; which is, in turn, why so many old Harlequin and Mills & Boon romances feature encounters that we'd now class as non-consensual between the hero and heroine. It wasn't because the writers didn't understand rape: it was because they were writing in a time where women were taught that wanting sex made them harlots, such that it was difficult for them to fantasize without shame. The hero knowing what the heroine "really" wanted and giving it to her despite her protests was a loophole.
I could go on, but the key point is this: given that nobody on Earth can perfectly control their own arousal, it is imperative to acknowledge that being turned on by something doesn't mean wanting it in real life, because the alternative is forcing yourself to choose between sexual shame and justifying it in real life. And neither of those things has ever led anywhere good.
