Demonstrably true.
In a broadside printed in 1858, Spooner spelled out how such a right could be exercised. First, groups should form in the North to send arms, aid, and even to fight in the South. Groups of Black citizens in the South should also "form themselves into bands, build forts in the forests, and there collect arms, stores, horses, everything that will enable them to sustain themselves, and carry on their warfare upon the Slaveholders." Such guerrilla forces could (until the anti-slavery forces were strong enough for outright war) capture, strip and flog individual slaveowners, in front of their slaves in order to undermine the masters authority. These forces, North as well as South could live by robbing the slaveowners...When John Brown failed and was imprisoned, Lysander Spooner made another proposal for a guerilla action. He suggested the capture of Governor Henry Wise of Virginia, who could be held hostage for Browns release. Spooner planned an attack by sea through the Chesapeake Bay and James River; this area was already a haven for runaway slaves, smugglers, and others outside the law. A group could reach Richmond, the state capital, and kidnap the governor on his evening walk; once out to sea, they would be relatively safe. John LeBarnes wrote Thomas Wentworth Higginson, November 15, 1859, "LS [Lysander Spooner] called upon me yesterday. His idea has certainly the merit of audacity."
http://www.lysanderspooner.org/BIOch5.htm
I don't think so.
States built on gross and direct violations of human rights (be it totalitarianism,
communism, slavocracy or Naziism) have no "right to exist" and it is within the self-defense rights
of free men to prosecute them as they would a common criminal.
Spooner was moral. Freeing slaves, even by murder was moral.
You however, are not.