Garrison worked very closely with the African-American abolitionists even before he started The Liberator. In fact, that community's support helped to keep him safe and in business, especially in the first ten years of the paper (they often sent people to guard Garrison, who was a passivist and refused to carry arms, when he was going home from meetings). Of course, Douglass also became a leader in the movement but I don't know whether his break with Garrison significantly affected their role in society or helped after the civil war. The Black Abolitionist Project on ProQuest has gathered together the writing of 300 of the African American abolitionists who were active in publishing during the years of 1830-1865. That would be a good place to research these questions.