Society views incest is wrong because the vast majority of people have the natural human instinct to avoid incest. You'll find most higher animals also have similar instincts.
Only if there is a wide selection of potential mates about. Which isn't\wasn't true in many societies. And even then your claim is dubious... It is 'wrong' because it represents "Closedness" to the world. It's interesting to note most of things the society considers Paraphilias Incest is the only one isn't considered related to Urban Bohemians but rather Rednecks.
* - If you want to be really technically, every single sexual relationship is incentous as every human being is related via the same Mother going back when Homo Sapiens were a minor tribe of hominids in the Sands of East Africa.