The murder of abortion doctor George Tiller in Wichita, Kansas set off kilotonnes of controversy in the media this week. President Obama was outraged: "However profound our differences as Americans over difficult issues such as abortion, they cannot be resolved by heinous acts of violence."

Dr Tiller was one of three American doctors who were willing to do late-term (after 21 weeks) abortions. For years he had been reviled by anti-abortion groups. Over the years his clinic had often been vandalised and in 1993 a woman shot him in both arms. He survived this violence as well as court challenges to his work. In March he was found not guilty of 19 misdemeanour charges after a widely publicised trial. Political commentator Bill O'Reilly used to call him "Tiller the baby killer" on his radio show.

On May 31, during a service at the Reformation Lutheran Church Tiller was shot in the head, allegedly by 51-year-old Scott Philip Roeder, a divorced odd-jobs man with a history of psychiatric illness and association with anti-government militias. Apparently he was not a member of any established anti-abortion group.

Although there are extremists who believe that killing abortion providers is justifiable homicide, they are a tiny fraction of the US anti-abortion movement. The best-known groups all issued statements deploring the murder. A comment from the National Right to Life Committee is representative: "The pro-life movement works to protect the right to life and increase respect for human life. The unlawful use of violence is directly contrary to that goal."

However, supporters of abortion were quick to claim that "the bloody, homicidally drenched terminology" of the anti-abortion movement triggered the assassination; terms like "holocaust" and "genocide" were bound to push unbalanced supporters over the edge. Some taunted pro-lifers by contending that if they really believed that abortion was murder, they are morally obliged to kill abortionists. But since they don't, they are cowardly or insincere.

What happens now? Tiller's murder has been a serious public relations setback for the pro-life movement, but it could be just temporary. After all, the killer has been disowned by everyone in the pro-life moment. A voluntary decline in incendiary language would be one welcome outcome -- imposing limits on abortion rhetoric in the US seems unlikely.

Another advance could be clarification of the terms of the debate between the two "irreconcilable" sides, in the words of President Obama a few weeks ago in a speech at Notre Dame. In one of the few measured reflections on the murder, Megan McArdle, of Atlantic magazine, argued that it is becoming clear that the abortion debate is about what it means to be a person, not about women's rights.

It seems to me that really broad swathes of the pro-choice movement seem to genuinely not understand that this is a debate about personhood, which is why you get moronic statements like "If you think abortions are wrong, don't have one!" If you think a fetus is a person, it is not useful to be told that you, personally, are not required to commit murder, as long as you leave the neighbors alone while they do it...

More controversially, she suggests that the murder may indicate a failure of the political process:

If you interpret this murder as a political act, rather than that of a lone whacko, than this should be a troubling sign that the political system has failed. So why do so many people think that the obvious answer is simply to more firmly entrench laws that are rightly intolerable to someone who thinks that a late term fetus is a person?