John brown was a hero .He faut for what he believed in and that's all that matters.
(So did Hitler and the Al Qaeda skyjackers!)
He murdered a number of people over their politics. He performed a terrorist raid on the armory at Harper's Ferry. Anyone who agreed with his views, then, would have his crimes thrown up at them. "That is the sort of people Abolitionists are", that sort of thing. Doing more harm than good does not make you a hero.