The Autobiography of Frederick Douglass, a former slave, is well worth reading if you have not already done so.  Douglass thought highly of John Brown, the firebrand abolitionist, who determined violent means were justified to achieve worthy goals.  Ironically, Douglass understood something that Brown did not: the pen is mightier than the sword.  Here is the commentary of Douglass upon the death of Brown:

“With the Allegheny mountains for his pulpit, the country for his church, and the whole civilized world for his audience, John Brown was a thousand times more powerful as a preacher than as a warrior.”

(As quoted in Allen Guelzo, Fateful Lightning: A New History of the Civil War and Reconstruction, p. 118).