How did David Walker build an argument against slavery and in support of abolition?

Having witnessed slavery and racism, he wrote an 1829 pamphlet, Appeal to the Colored Citizens of the World that urged African Americans to fight for freedom and equality. Walker was decried for inciting violence, but also changed the abolition movement

Explanation:

The goal of the Appeal was to instill pride in its black readers and give hope that change would someday come. It spoke out against colonization, a popular movement that sought to move free blacks to a colony in Africa. America, Walker believed, belonged to all who helped build it.

the best description of postwar writers might be progressive.

following the war, writers showed a tendency to work on artistic or social matters rather than political themes. while postwar literature may not have been the greatest period of english literature, the themes provided excellent critics a high number of novels. such examples include anthony burgess, anthony powell and frank kermode, all of which can be placed under the progressive view.