Final answer:
Frederick Douglass's advocacy for a composite nation and equal treatment was fundamental to the ethos of the Civil Rights Act of 1875, whose nullification in 1883 by the Supreme Court resulted in the rise of Jim Crow laws, perpetuating the civil rights struggle.
Step-by-step explanation:
The incident involving Frederick Douglass is linked to the Civil Rights Act of 1875 through his advocacy for a composite nation that embraced diversity and equal treatment for all races, which was a foundational concept behind the act. After the Supreme Court declared the act unconstitutional in 1883, this setback allowed segregation to persist until it was challenged again in the civil rights era. Douglass, along with other leaders like Charles Sumner and the efforts of African Americans through lawsuits, highlights the ongoing struggle for civil rights from Reconstruction to the Civil Rights Movement of the 1960s.