Why is the song "Beasts of England" banned?

In Animal Farm, the song "Beasts of England" is banned because Napoleon’s regime fears its revolutionary power after the pigs become the new oppressors.

The immediate official reason comes after Napoleon’s executions of the animals who supposedly conspired with Snowball. Clover and the others, shocked and grieving, gather near the windmill and sing "Beasts of England" mournfully. Squealer arrives with two dogs and announces that the song is no longer needed because the rebellion has been completed and the traitors have been punished. In other words, the animals have supposedly already achieved the free society the song imagined.

The real reason for the ban is darker. "Beasts of England" once united the animals against Mr. Jones by giving them a shared vision of freedom, equality, and life without human tyranny. After the executions, that same song becomes dangerous to Napoleon because the farm now resembles the old tyranny again. Clover recognizes the contrast between the original dream and the present reality: she had imagined “a society of animals set free from hunger and the whip, all equal, each working according to his capacity, the strong protecting the weak[.]” But instead she sees a farm where no one dares speak freely and where animals are unfairly punished or even killed.

The ban is enforced through fear and propaganda. Some animals think of protesting, but the sheep drown out discussion by bleating “Four legs good, two legs bad.” Minimus then writes a weaker replacement song praising Animal Farm itself, shifting loyalty away from revolutionary ideals and toward the state Napoleon controls. The ban marks the moment when the language that once helped free the animals is censored because it might help them recognize their oppression again.