Why do the Watsons not like the music in the South in The Watsons Go to Birmingham—1963?

In The Watsons Go to Birmingham—1963 by Christopher Paul Curtis, the Watson family takes a trip from Flint, Michigan, to Birmingham, Alabama, Mom’s hometown. Dad tells Kenny that the only music played on the radio in the south is hillbilly music. By hillbilly music, Dad means country music. Country music is associated with the south. Dad says that he and Momma have jokingly promised to divorce each other if either one starts listening to country music. Ultimately, Dad buys the Ultra-Glide True-Tone AB-700 for the car so the family can listen to the music they like all the way to Alabama and do not have to listen to the radio at all. The Ultra-Glide is basically a record player for the car. All of the children are allowed to bring their favorite records on the trip. It becomes a source of joy for the family and brings them closer together.