You really don't think it would have been justified for a slave to kill his master? Maybe we're on a different page here.
To me, it's justified in the same way a North Korean in a labor camp would be justified killing his guard.
And anyway you have a great point obviously bo_sox, and the title is simply meant to be provocative.
But as Socrates is saying, when you really think for a second about what continued slavery entailed for the four million black slaves in the south, it becomes hard to say that the violence of John Brown was unjustified. In fact, it even invites the question as to whether he was the only one doing the right thing.
There are very few modern equivalents to this type of thing, and even such that those things exist, without the benefit of hindsight we cannot really know what they are.
The point of John Brown from a modern perspective is that he was possible, as one historian put it "the most perceptive American of his generation."
That is to say - while nearly every one of his countrymen, even the moral abolitionists, were content to allow slavery to continue into the future, he did what he could to end it right away. If a few thousand whites were to die in that pursuit, which I'm sure he expected to happen, would it not be justified still?
I mean, we today know that the American slave trade cost the lives of millions of blacks. Putting an end to that would seem to be imperative.
The comparison with other countries is rather null. Slavery in the UK was nothing like what it meant for American Southerners.
It does make one wonder what modern "extremists" future generations will vindicate. Abortion clinic bombers, suicide bombers, rebel leaders... hard to say for sure of course. The lion's share of such violence is senseless.. but it would be painting with too broad a brush to claim that violence is never justified, wouldn't it?