Final answer:
W.E.B. Du Bois viewed Marcus Garvey as an adversary due to their opposing ideologies, with Du Bois favoring civil liberties and legal challenges to segregation through the NAACP, while Garvey emphasized economic self-reliance and a separate black community.
Step-by-step explanation:
W.E.B. Du Bois considered Marcus Garvey a significant adversary in the struggle for racial advancement in America primarily due to differences in political ideologies and strategies. Du Bois was a proponent of full civil liberties, utilizing legal channels through organizations like the NAACP to challenge segregation and advocate for social justice. He believed in the importance of political and social equality and the necessity of educating African Americans to become leaders. In contrast, Marcus Garvey focused on economic independence and self-reliance, with less emphasis on integration and more on the establishment of separate institutions for black people, including the support for African Americans to return to Africa. Garvey was critical of the NAACP's strategy to integrate African Americans into white-dominated institutions, which he found counterproductive to racial advancement.