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...Well, I meant direct siblings and parents - cousin marriages have been rather common throughout history for the reason you stated above. Sibling/Parental incest is generally considered disgusting and therefore "wrong" due to our instincts, but I'd say the stigma against cousin incest is mainly a cultural phenomenon.
