Back in the good old days when society was more Christian, homosexuality was a major taboo. Homosexual sex was seen the same way as incest, a morally reprehensible perversion.
However with a decline of Christianity, homosexual sex became accepted, and now there are same sex marriages.
Since people don’t see homosexual sex as a perversion, what’s going to stop them from not seeing incest as such? Since people stopped becoming repulsed by homosexuality, I predict in the future that people will stop being repulsed by incest and it will become accepted in society. There will be brother-sister marriages, brother-brother marriages, sister-sister marriages, mother-son marriages, mother-daughter marriages, father-daughter marriages, and father-son marriages.
This is why society needs a return to Christianity to prevent my predictions from coming true.