Final answer:
The phrase "states' rights" is a misnomer because it was used as a cover for racial prejudice and the defense of slavery.
Step-by-step explanation:
The phrase "states' rights" is considered a misnomer because it was often used as a cover for racial prejudice and the defense of slavery. While proponents of states' rights argued for greater local control, they often used this argument to oppose civil rights and federal interference in issues such as school desegregation. The term has been associated with the historical context of the Civil War and its aftermath, where southern states used it as a justification for secession and the preservation of slavery.