Ayers was a leader of the Weather Underground (aka the WUO, aka The Weathermen -- don't get on my case about the name changes and timeframe, ok), an organization that carried out symbolic bombings against property -- the key point that all reports on the WUO seem to leave out is that the WUO took great pains to ensure that their bombings did not cause physical harm to living people. In fact, the only three people to die from WUO bombs were WUO members. They were not carpetbombing civilians in Cambodia. They were not firing on unarmed college students.
What do you do to stop a war? Do you try non-violence only? Or do you go with Malcolm X's dictum of "by any means necessary"? In the face of continued oppressive violence -- when it's obvious that you are functioning within an economy of violence -- does it not make sense at some level to respond in a way that "brings the war home" as the Weathermen (and SDS) put it?
The answer, for me, is maybe. It's not an absolute; you have to contextualize, historicize. That's exactly what Thoreau did between his widely-known essay "Resistance to Civil Government" (1849) and his lesser-known and later "A Plea for Captain John Brown" (1859).
In the former essay, Thoreau is committed to what we understand as traditional non-violent means:
In fact, he calls this resistance a "peaceable revolution." Yet as a decade rolls on and it seems that the state has no interest in stopping slavery -- as slavery seems destined to roll through the newly acquired territories -- Thoreau changes his tune. In his impassioned response to John Brown's failed raid on the federal arsenal at Harper's Ferry, for which John Brown and his Black and white comrades were condemned to die, Thoreau makes clear that there are limits to non-violent responses:
Cast your whole vote, not a strip of paper merely, but your whole influence. A minority is powerless while it conforms to the majority; it is not even a minority then; but it is irresistible when it clogs by its whole weight. If the alternative is to keep all just men in prison, or give up war and slavery, the State will not hesitate which to choose.
It was his peculiar doctrine that a man has a perfect right to interfere by force with the slaveholder, in order to rescue the slave. I agree with him. They who are continually shocked by slavery have some right to be shocked by the violent death of the slaveholder, but no others. Such will be more shocked by his life than by his death. I shall not be forward to think him mistaken in his method who quickest succeeds to liberate the slave.Thoreau is clearly advocating intervention "by force" on the side of abolition. Furthermore, he makes clear throughout the essay that a government that countenances the violence of slavery should be met with violent resistance. Does this make Thoreau a terrorist sympathizer? Or is Thoreau simply following true to the doctrine that some Americans subscribe to that holds that "when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism it is their right, it is their duty, to throw off such Government."
Again, there's nothing universal about it -- it's situational (I mean the document discusses a pattern that "evinces a design to reduce them under absolute despotism," not the actual reduction to a state of absolute despotism -- there's plenty of room for judgement calls), and I'd argue that in the face of the overwhelming unethical violence of chemical warfare, carpet bombing, and domestic assassination, it's utterly hypocritical to judge symbolicly placed, non-injurious bombings on the level of terrorism.
That stance does not open the door to defending every newspaper kiosk thrown through a Starbucks window or the assassination of executives of companies whose hired help executes labor activists.