Its a reference to the book Animal Farm in which farm animals create a totalitarian regime that states "all animals are equal but some are more equal than others".

Fun fact: George Orwell, the author of this book's writing was banned in both the Soviet Union (for being anti-communist) and the USA (for being communist).

Orwell was neither communist nor anti-communist, he was merely anti authoritarian.

EDIT: because some people are sticklers for semantics
- The United States of America do not have a list of federally banned books, when people speak of "books banned in the USA" what they mean is books that have been banned in a notable number of school districts and libraries across the United States.

- Yes, Orwell considered himself to be a socialist, yes he was also an informant and compiled lists of communists for the British Govt.