The song is a parody which also draws on traveling salesmen jokes, where the main character shows up at a farmhouse looking for a place to spend the night, only to be lured by the temptations of the farmer's daughter.
Wanting to flee but feeling obliged to stay and milk the cow as promised, the narrator shouts out one of the most offensive things he can think of: that he likes "Fidel Castro and his beard".
[3] When Dylan wrote the song, at the height of the Cold War when Soviet communism was regarded as the number one threat to the USA, Castro, who set up a communist government in Cuba in the early 1960s was viewed as one of the country's principal enemies.
The implication of the song is that even the most outrageous political statements are protected by the First Amendment, and as Dylan's character realizes, exercising that right in this case possibly saved his life.
Wilentz argues "115th Dream" shares "an identical melody" with "Motorpsycho Nitemare" and both songs revolve around a hapless traveling salesman who is constantly "getting in and out of jams".