John Brown was insane. Just about all his relatives were insane. In Eastern, Kansas he murdered a slave holding family including young boys and chopped their bodies into pieces.
I agree completely that Brown was a homicidal maniac.
Though it is interesting to note how powerful the Bowie knife was in the “collective consciousness” in both the South and the North. This began in 1827, at the notorious Sandbar Fight, which even in retrospect, was one hell of a fight.
http://en.wikipedia.org/wiki/Sandbar_Fight
So though northerners, southerners, and even blacks saw the knife from different perspectives, it was seen as the weapon to have in a brawl.