I just read a couple of whines from people who find incest to be equally as disgusting as pedophilia and bestiality and demanded to know why it was more accepted than pedophilia or bestiality. Since I'm just about the only person on Earth who can explain it, I will endeavour to do exactly this.
Yours vs Mine
First of all is the observation that people who like incestuous fiction frequently declare their own revulsion at the thought of having sex with any of their real life actual family members. As near as I can tell this is unique to incestuous stories and doesn't happen with bestiality or cannibalism fetishists.
People who read or write stories featuring pedophilia have an entirely different excuse to give when they bother to give an excuse. At least the ones who aren't insane and try to justify the real life activity. Rather than claiming that they would never do this with THEIR children, they draw the line at fiction vs non-fiction.
These distinctions are important because in your brain, there are entirely different concepts for the concrete "my car", the abstract "this kind of car", and the more abstract "a car". So while people are attracted to abstract-incest, they are revolted by concrete-incest.
The reason this is so is rather simple. There is a biological mechanism that turns you off from people you're overly familiar with. This USUALLY kicks in during adolescence when you become turned off from the people you grew up with. People who just so happen to share your genetics most of the time. Idiots then conclude that there must be an "incest taboo" and that fucking people with your genetics is Wrong.
They do this because being idiots they confuse genetics with grew-up-with. And then they generalize their revulsion from the concrete to the abstract. This is how Right-Wing Authoritarian idiots (wannabe Nazis) who make up 25% of the American population, have concluded such a ludicrous thing as the "incest taboo" exists, despite all the overwhelming evidence to the contrary.
In their minds, it's normal for your family members to share your genetics. And it's normal for people you grew up with to trigger overfamiliarity revulsion. Therefore, it's normal for people who share your genetics to trigger revulsion in a sexual situation. It's the RWA idiot's version of "logic" and is as simple to them as 7+13 = 20.
No Repulsion
However, that's clearly not how it works for others. Who perhaps aren't such idiots that they confuse genetics with grew-up-with, although most likely they are. No, the reason why they're not bothered by incest in the abstract is because they never generalize their revulsion in the first place. At least not in that direction. Perhaps because their brain ascribes being turned off by people they grew up with to their being old and wrinkly, or having mean personalities, or even being Evil.
Why should a child be sexually attracted to an ugly parent? Why should an anarcho-communist child be attracted to a right-wing authoritarian parent they're constantly fighting with? It doesn't make any sense. Rather, it makes sense that they aren't attracted and so there is no need to reach for any kind of more strenuous explanation such as "abstract-incest is yucky".
This explains in full why most people aren't disgusted by incest in the abstract while being repulsed by the thought of themselves practicing incest. Because most people aren't Right-Wing Authoritarians to orient their entire lives around Social Norms. And most people just don't feel the need to create false generalizations, or simply aren't any good at generalization.
It doesn't end there.
Positive Attraction
Because you see there is an OPPOSITE force that makes people ATTRACTED to the idea of abstract-incest. That force is confusion of romantic love with sexual love, of intimacy with safety.
That last is the reason why modern humans have developed a sexual fetish for plushies that had never existed before. Note also the critical importance of there not being any widespread concept that over-familiarity is a turn-off in itself as it is in actuality. If such a concept were widespread then the incest fiction would die out, except maybe for Narcissists. The same way rape fantasies (and rape itself) have largely died out.
Because sexual attraction can be turned off at any level of the mind. Something you can see in highly moral people who are revolted and turned off by catastrophists (rapists, killers, doomsayers, warmongers). Or by right-wing authoritarians (who misuse the word "morality" to mean social norms) who are revolted by deviants and freaks.
But sexual attraction ORIGINATES in the deepest level of the mind. Specifically, the part-objects level. It's the reason why disconnected body parts like tits and asses and pussies and cocks and legs and arms and feet have the power to turn anyone on. Meanwhile, romantic attraction originates in ... the SECOND-deepest level of the mind, the pair-bond level. And the whole concept of 'family' originates in ... the THIRD deepest level of the mind, the subcomponent level.
There are 11 levels in the human mind and the incest fetish, or even just finding it a turn on, is confusion between level 1, 2 and 3. Out of 11. Seen that way, it's pretty fucking predictable that abstract-incest would acquire a positive value. And equally predictable that this positive value would survive conflict with the negative value of concrete-incest.
Confusion And Distinction
Especially since human brains are quite capable of drawing a distinction between rain water, river water, saltwater, shower water, toilet water, sewage water, distilled water, reverse-osmosis water, drinkable water, H2O and water water. Despite the fact that ALL of them LOOK identical and most of them even feel and taste identical..
If you're the kind of retarded idiot that can't draw a distinction between abstract-incest and concrete-incest then I dare you to drink toilet water. After all, it's no different from drinkable water, is it?
Finally, regarding cannibalism fiction. How can you regard yourself as an educated citizen of the world if you don't know what motivates black Africans? Although for black Africans, cannibalism is rarely sexual and more likely to be about the acquisition of magic powers.
Fuck, I bet this article will get me chaff from inbred yokels who don't even know what the word 'intersexed' means. You know the kind, the ones who titter nervously at those articles describing how tigers have barbed penises and ducks have twin penises and so on. Rather than lift an eyebrow in very mild interest then flip the page over. RWA fucks.