Why was "What the Black Man Wants" by Frederick Douglas a significant speech in American history?

The speech was given within days of the close of the Civil War and the assassination of President Lincoln. Douglass argued in favor of suffrage for Blacks, as well as equality, rather than generosity. The significance is how incredible it was at this time in history for a black man to stand up and speak about equality and freedom. He did so with the power of words and not violence. People listened. Even President Lincoln.