A project I'm currently working on features two attempts at rape so I'm naturally alright with creators including it. Personally, I wouldn't even include trigger warnings if that wasn't such a huge thing online. I probably won't for the paperback issue since I feel that a story should stand on its own and not need additional texts like that. I'm pretty sure readers will be able to see the attempts coming from a mile ahead anyway since it ties into the bigger themes of the story.
That said (and I hope I'm not adding to the previous drama with that since I'm basically agreeing with what @Adeca wrote originally) even if there is a trigger warning, I still feel that readers can complain about rape being included in the story.
I might also feel this way because I grew up mostly reading paperback and only switched to online reading in the past couple of years. Back then, nobody had tags or content warnings and even now, I often don't look at tags since I don't want to know before reading what happens in the story. It would take away from my enjoyment if I did.
There are still elements I don't like in stories and if I'm in the mood to comment, then I might complain about them when they appear. That doesn't mean that the story is bad because of that or that I don't think the creator shouldn't have included them/is a bad person/whatever but just that at the moment when I read that I didn't like what I read. It's the same whether it's rape or harem or some trope I think is overused. At that moment, I'm just giving my opinion as the reader. I don't expect the creator to read or interact with that opinion or have the same opinion as me but I feel that it's alright to state it.
Rape is is a sensitive issue so the readers' comments might get more heated and the creator might feel that they are only getting this backlash because it's rape (I actually think @JRHoch's comparison with murder as a plot device was interesting. There sure isn't a reaction as strong to that as to rape). But on the other hand, creators get backlash for almost anything. Heck, I've gotten complaints from readers because they didn't like the personality of the main character of a project I had.
To me, both these complaints are the same: I wrote something the reader didn't like, the reader told me, and that's it. They might stop reading or continue the story but that's out of my hand. I can interact with their reaction or let it be and that's it as well. It won't change the story I wrote, it likely won't change their perception and it likely won't change my stance on things. It's just a comment like every other one as well.