Granted. Without questioning their intent anymore, people gradually start to ignore them more, and a great number of car accidents happen with chickens.
Granted, roads are clogged with an endless amount of chickens and nobody can go anywhere by land. Humanity has to move to space in 13 different space stations, and eventually the space stations merge after the 13th was blown out of the sky. 200 years later, they send 100 juveniles to Earth to see if the chickens have gone extinct and repopulate.
Granted. As a result of one of the classic jokes being removed, dads around the world have less ways to introduce children to comedy. The world is overall a sadder place.
Granted. Humans no longer question which came first, chickens or eggs. Humans no longer analyze any form of cause and effect whatsoever, and make their decisions based on whatever they last saw on the internet. This takes effect immediately prior to the 2016 election in the United States.
Granted. One day a chicken gets fed up with the questions and murders 5 bystanders on the street. After this noone dares to question chickens.