On a recent night, while I was waiting for my daughter to get out of play rehearsal, I flipped the car radio to our local NPR affiliate. Fresh Air was on, and the host, Terry Gross, was interviewing William Ayers.

After a minute I was hooked. And then I was mesmerised.

I hadn't expected to be. During the presidential campaign I had no particular interest in the aging radical. Ayers was, as he told Gross, "a cartoon character or a caricature that was thrust up on the stage" for the sole purpose of damaging Barack Obama. Sarah Palin's accusation that Obama had been "palling around with terrorists" was an offensive lie, which is to say it was business as usual for the most negative, dishonest campaign in several decades. As for Ayers himself, though, who cared?

Ayers made me care. He came across as intelligent, sympathetic, multi-dimensional and reflective - in other words, like an actual human being. He expressed regrets about his 1960s radicalism, though in a selective and self-regarding manner – again, like a human being. And if he's not quite the wonderful person he portrayed himself to be – indeed, his limited contrition seemed artfully designed to underscore his wonderfulness – he nevertheless convinced me that his crimes were minor compared to the useful life he has led.

Which makes it all the more reprehensible that John McCain and Sarah Palin would single this man out, holding him up as an object of hatred as the crowds they had whipped into a frenzy cried, "Kill him!" The McCain-Palin ticket may be history, but the rage it unleashed lives on.

"Now that the campaign is over, have the death threats stopped?" Gross asked Ayers.

"Escalated," Ayers replied.

"Why, do you think?"

"I'm not sure," Ayers said, "but I've gotten a lot of threats that talk about civil war and the fact that we now have a socialist government and that the war is on. And I send all of these threats to the police because I don't know how to handle them".

Ayers's notoriety is not new. A founder of the Weather Underground, a radical antiwar movement, Ayers is perhaps best known for a quote that appeared in the New York Times, infelicitously enough, on September 11, 2001: "I don't regret setting bombs. I feel we didn't do enough." Ayers told Walter Shapiro of Salon recently that the Times misquoted him on the matter of bombs. Still, it's a matter of record, which Ayers doesn't deny, that the Weather Underground bombed the Pentagon and the Capitol.

Yet the group apparently stuck to its non-lethal aim, as Ayers explained to Gross, of targeting property rather than people. The worst that ever happened was when three members of the group themselves (including Ayers's then-girlfriend) were killed by a bomb they were making in Greenwich Village. Other than that accident, the radicals neither killed nor injured anyone - far more than could be said about the political figures of that era, or of this one.

Some dispute that assertion, which helps to explain why Ayers is more controversial than he should be. Here in Boston, many people believe the Weather Underground was responsible for the 1970 murder of a Boston police officer named Walter Schroeder. In fact, the radicals who were responsible for Schroeder's death, Katherine Ann Power and Susan Saxe, were not affiliated with the Weather Underground. Ayers also told Gross that the Times recently erred again by linking the Weather Underground to the murder of a San Francisco police officer that same year. According to Time magazine, the San Francisco bombing was "never conclusively attributed" to the group.

Such details matter, because they explain why Ayers was able to build a post-60s career as a respected education-reform advocate able to work with Democrats and Republicans alike – and who is able to get along, as he told Gross, with the police officers now charged with protecting his life and that of his wife, the former radical Bernardine Dohrn, from the violent impulses that McCain and Palin so casually and carelessly indulged.

By the way, the play in which my daughter had a small part was The Crucible, Arthur Miller's heavy-handed but powerful retelling of the Salem witch trials, meant at the time of its writing as an allegory about the McCarthy-era persecutions. It was fitting. McCain, who made personal honour the centrepiece of his presidential campaign, dishonoured both himself and the democratic process, much as Joseph McCarthy did a half-century ago.

But unlike McCarthy, McCain has already been welcomed back into polite company, as though his gracious concession speech could wash away his campaign's "moral filth", as Josh Marshall of Talking Points Memo has put it.

Thus it is the Ayers family that will continue to pay for McCain's dishonour. Sadly, it's a fitting end to an ugly chapter in American politics.