BOSTON — It is believed that the shooter acted alone.

Surely, that’s true. No one else was standing beside suspect Scott Roeder when it is believed he murdered Dr. George Tiller in the sanctuary of his church.

But Michael Griffin also acted alone when he killed David Gunn in 1993. Paul Hill acted alone when he killed John Britton in 1994. John Salvi acted alone and so did Eric Rudolph and James Kopp. This suspect is hardly lonely in this murderous cast of lone actors.

It was an isolated incident.

So it was. There was no grand scheme of assassinations. But it was also an isolated incident when Tiller’s clinic was first bombed in 1986. It was an isolated incident when he was shot in both arms in 1993. Each anthrax threat, each invasion, even the vandalizing that took place last month at his Wichita clinic were all linked in a daisy chain of “isolated incidents.”

The pro-life community reacted with shock.

No doubt. But where was the shock at the fringe groups they forgot to disavow? At the “Tiller Watch” page that Operation Rescue featured? At the postings by one Scott Roeder calling Tiller the “concentration camp Mengele of our day”? At the Defensive Action Statement that says murdering an “abortionist” is “justifiable”?

Were they also shocked by the everyday mainstream rhetoric that casually refers to abortion as murder? Did they worry about the movement strategy designed deliberately to target providers, the weak link of abortion rights, driving clinics out of 87 percent of our counties?

Pro-life leaders denounced the murder.

So they did. But how inconvenient that some of their own “stars” seemed less than mournful. That Randall Terry called Tiller a “mass murderer” who did something that “was literally demonic.” Or that the Army of God called the suspect “a hero.” Or that the “comments” on a rash of blogs piled vitriol onto the body of the late doctor. Or that Tony Perkins of the Family Research Council worried most that “what (Tiller) did is being glossed over.”

I have covered far too many such murders. As a First Amendment absolutist, I don’t believe that words kill. But this week, I can’t help wondering whether rhetoric can justify a crime in the mind of a fanatic. Can’t words provide the sort of perverse moral platform that jihadists stand on and the alternate universe in which a “lone nut” can find a home?

Consider the verbal targeting of “Tiller the Baby Killer” that preceded this assassination. What do you say, for example, about Bill O’Reilly, who attacked Tiller repeatedly as someone who would “kill a baby a half-hour before the baby is supposed to be birthed for no reason whatsoever other than the mother has a pain in her foot”? Or should we let O’Reilly say it himself? The unrepentant Fox News host boasts “no backpedaling here. … I report honestly every single thing we said about Tiller was true.” Except that it wasn’t.

I regret that, even in mourning, Tiller’s family cannot escape abortion politics. He was a doctor of last resort for many women, especially those women for whom the sonogram did not bring joy but tragic tidings. He refused to be cowed. At the very least, he should be buried with truth.

I don’t blame everyone who checks a pro-life box on the pollster’s chart. I know that ambivalence is the emotion often cast onto the sidelines of this debate. But it is well past time for the anti-abortion movement to denounce those who are in the profession of inflaming passions: Those who call Obama the “most pro-abortion president ever.” Those who ratchet up the rhetoric on a Supreme Court nominee. Those who cull doctors from their honored profession by labeling them “abortionists.”

At the Notre Dame commencement where Obama was picketed, the president asked, “As citizens of a vibrant and varied democracy, how do we engage in vigorous debate? How does each of us remain firm in our principles, and fight for what we consider right, without demonizing those with just as strongly held convictions on the other side?”

One way is for those who truly “denounce the murder” to take on the chorus, the back-up singers, who still provide the doo-wop for the next deranged soloist.

You see, this suspect was not such a lone gunman. And no, I am afraid, this was not an isolated incident.