Cutting music education would, first and foremost, take a dent out of public education expenses. The cost for musical instruments, practice time, travel costs and paychecks for music instructors would all be cut from the budget.
Not everyone is interested in learning how to play a music or in learning music theory. Eliminating music education in public schools would allow students still interested in music the option of taking private lessons, while students who do not care to learn wouldn't be forced to.
Some other teachers in the building complain about the loud noises from drums and other instruments that disrupt the focus and attention from the students in the classroom.
Some teachers and parents argue that if there is a music education department then every school should allow students to learn about film making, acting and other arts that are not an option at public schools. Cutting the music education department would dissolve some of that bias.
Some parents disagree with music education especially in early education because music theory and playing an instrument can be difficult. Students who struggle with music will likely receive a poor grade which hurts their GPA.