It was a
response to the crimes that proslavery men had been getting away with for some time -- including the cold-blooded
murder of a number of freesoil men. John Brown didn't even manage to tie the score. Yet the only deaths you appear to be aware of are those committed by John Brown. Why is that? (I'm not criticizing you, I'm saying you've been deceived by proslavery propaganda).
Here's a second example: in May of 1858 proslavery men rounded up 11 freesoil Kansans and shot them in a ravine along the Marais des Cygnes. No effort was made to arrest or punish the killers despite the fact that their identities were known; only one of them was ever even brought to trial. Later that year John Brown raided slaveholders in Missouri, freeing 11 slaves; one slaveholder who put up resistance was shot dead by Brown's men (Brown himself was not at the cabin in question). Mass hysteria swept the South and their sympathizers in the North and James Buchanan put a price on Brown's head.
Brown himself eloquently pointed out this hypocrisy in his "Parallels" (I'll excerpt -- you can read the whole thing at
http://www.plainandsimple.org/parallels.html):
"Not One year ago Eleven quiet citizens of this neighborhood... were gathered up from their work and their homes by an armed force and... formed into a line and all but one shot, five killed and five wounded. The only crime charged against them was that of being free-state men. Now, I inquire, what action has ever, since the occurrence in May last, been taken by either the President of Kansas, or any of their tools, or by any proslavery or administration man, to ferret out and punish the perpetrators of this crime?
"Now for the other parallel. On Sunday, the 19th of December, a negro called Jim came over to the Osage settlement from Missouri and stated that he together with his wife, two children and another negro man were to be sold within a day or two and begged for help to get away. On Monday (the following) night, two small companies were made up to go to Missouri and forcibly liberate the five slaves together with other slaves. One of these companies I assumed to direct....
"Now for a comparison. Eleven persons were forcible restored to their natural and inalienable rights, with but one man killed, and all 'Hell is stirred from beneath.' It is currently reported that the Governor of Missouri has made a requisition upon the Governor of Kansas for the delivery of such as were concerned in the last-named 'dreadful outrage.' The marshal of Kansas is said to be collecting a posse of Missouri (not Kansas) men at West Point in Missouri, a little town about ten miles distant, to 'enforce the laws.' All proslavery, conservative free-state, and dough-faced men, and administration tools, are filled with holy horror.
"Consider the two cases, and the action of the administration party."