I don't get what some people's deal is with rape or other questionable content in a work of fiction.
I mean you're reading a continuation of a story that is clearly labelled with a "rape" tag. Chances are you aren't blind and have seen that tag. If you absolutely detest it, why would you read it anyways? You'd have to be incredibly masochistic, in which case you'd actually enjoy it, or just bored. Or you're trying to apply your morals on a pornographic fiction just for the sake of seeming morally just, which always baffles me when people do that. It seems like such a silly and pointless thing to do.
Basically, what you demand by saying that [insert tag here]-stories are sick and shouldn't exist, is censorship. Nobody likes censorship.
If I see any scat tags on a story, I likely won't read it and move on to other stories which I am more likely to enjoy. Or perhaps I will still read it since I am intrigued by another aspect of it, like the art, author, other fetishism etc., but even then, I won't go into the comment section and remind people of how much I dislike scat. That would be annoying for anyone who actually enjoyed all of it and in no way constructive critcism.
You didn't like it/feel grossed out? That's perfectly fine. Make a mental note and avoid similar stories in the future, saves you the trouble of reading something you dislike.
The folks that read such stories are likely into that fetish, they know the risks of applying it to the real world. Neither I nor anyone else is their nanny and has to remind them.
Sometimes, when I browse the comments of rapey stories here, I feel like I'm not on a site for lesbian goodness, cuteness and fetishism, but in the SJW pit of tumblr.