That gives me a little more persepective on where you're coming from. I myself am conflicted on the issue and still struggle with it -- sometimes we don't really know how we'll respond until the situation presents itself.
What still confuses me is not the immediate "self-defense" part of you question but the "OR" part you added, "But did any of them have nuanced--even conflicted--attitudes about violence as a means for self-defense
OR a way to resist political brutality and injustice?
See, it's the "or" part where you can head down a slippery slope. How does one define a political injustice that merits a violent response? If you asked John Brown, he would have said, ". . . I believe to have interfered as I have done, . . . in behalf of His despised poor, was not wrong, but right. Now, if it be deemed necessary that I should forfeit my life for the furtherance of the ends of justice, and mingle my blood further with the blood of my children, and with the blood of millions in this slave country whose rights are disregarded by wicked, cruel, and unjust enactments, I submit: so let it be done."
But John Brown was also known to have killed in retribution, not self-defense:
Despite his contributions to the antislavery cause, Brown did not emerge as a figure of major significance until 1855 after he followed five of his sons to the Kansas territory. There, he became the leader of antislavery guerillas and fought a proslavery attack against the antislavery town of Lawrence. The following year, in retribution for another attack, Brown went to a proslavery town and brutally killed five of its settlers. http://www.pbs.org/wgbh/aia/part4/4p1550.htmlConversely, those who lived in slave-owning states thought they were right to fight what they considered the political injustice of emanipating slaves. (And I do not intend here to debate whether or not slavery was the primary cause for Southern succession, though many neo-confederates would argue otherwise.)
Of course, it is always convenient to have the benefit of history and hindsight when it comes to making judgments about past injustice and who was right or wrong. The picture gets a bit more cloudy when we find ourselves in the midst of our own political struggles in a contemporary world.
Let's compare the Kansas actions of John Brown, say, and the current "war on terrorism". Was Mr Brown, otherwise nobly committed to the abolition of slavery, right to use violence in his defense of Lawrence, Kansas when it was attacked by pro-slavery guerillas? We could argue that this was certainly a case of self-defense, and draw comparisons to our invasion of Afghanistan post 9-11. But then we could go further and question Brown's brutal murder of settlers in a pro-slavery town in retribution -- is this the equivalent to one of Mr Bush's "pre-emptive" strikes against Iraq, which had not been involved in the 9-11 attack? Mr Bush certainly claims our invasion to have been one of pre-emptive self-defense though the evidence would show otherwise, and thousands of civilians -- men, women and children -- were killed.
Once you claim the right to violence on the grounds of fighting "political injustice" just where does one draw the line? There are some religious fundamentalists and anti-choice advocates who have claimed such right in their bombings of abortion providers and gay bars. When Mr Bush claims that "activist judges" are responsible for the marriages of gay folks in cities around the country, he is in essence claiming a "political injustice" has been done, as would gays who have been denied the right to marry. Could such a divide lead to a violent confrontation, each side claiming the right to defend themselves against a political injustice? ( I am a gay person, BTW, but a believer in non-violent civil disobedience.)
Anyway, I've barely scratched the surface of a very complex issue but have prattled on long enough. But I did feel I had to differentiate between an act of immediate "self-defense" committed during a violent confrontation and what might be argued as self-defense on the grounds of "political injustice" which you had mentioned in your original post. There are really several different arguments here each deserving of their own debate.