I think an issue with people who can't understand fetishes is that sometimes suspension of disbelief may fail. They're not suspending their beliefs so they have a hard time experiencing things how others usually would, so instead they think in a more rationale way despite it being fictional; which is illogical, but it doesn't need to be logical because it's fictional and an author's work does not have to be realistic. It only has to be believable. When the author pushes an audience beyond what they're willing to accept, the work fails in the eyes of that particular audience. Viewers are usually willing to go along with creative explanations for things.
But in this case, two worlds are colliding. May IIIII stand unshaken... Ammiddsttt. Amidst a crash of worldsss... If you got a guy who usually posts tentacle porn then he suddenly switches to gore, yeah I get that feeling.