The norm for protests over a William Ayers appearance on campus these days is for conservative critics to say that the University of Illinois at Chicago professor shouldn't be given a forum to speak because of the past violence of the Weather Underground, of which he was once a leader.
At Boston College, the debate has taken a new twist -- with the college calling off a talk by Ayers planned for tonight and citing a police killing that has never been definitively linked to the Weather Underground and that Ayers and others insist his group had nothing to do with. Nonetheless, that 1970 police killing is still associated by many in Boston with the Weather Underground and remains a political flashpoint -- as became clear on Friday.
Michael Graham, a local talk radio host, started calling on Boston College to revoke the invitation to Ayers, and he encouraged alumni, donors and others to call the college to demand that it deny Ayers a forum. Graham repeatedly linked Ayers and the Weather Underground  to the 1970 killing of Walter Schroeder, the police officer, who was responding to a bank robbery by a group of radical students. Schroeder left a wife and nine children. His killing is periodically back in the news, and last received extensive coverage in 1993, when Katherine Ann Power -- one of those involved in the incident, who had evaded capture and lived under another name -- turned herself in. 
Notably, the Weather Underground claimed credit over the years for plenty of incidents and its one-time leaders like Ayers who have since disavowed violence have admitted that the group did commit illegal and violent acts.
But the Weather Underground never claimed credit for the robbery and killing in 1970, and those involved have said that they were trying to get money for the Black Panthers, not the Weather Underground. (Dan Kennedy, an assistant professor of journalism at Northeastern University, and blogger on Boston media issues, over the weekend posted two items detailing all of the evidence suggesting that the Schroder killing was not the work of the Weather Underground -- see items here  and here.  Graham responded by calling Kennedy "some moron who claims to teach at Northeastern University.")
Boston College issued a statement in which it acknowledged barring Ayers, who had been invited by two student groups to talk about education reform (the focus of his work as a professor). "As a university, we pride ourselves on the free expression of ideas and on the prestige that Boston College holds as a destination of choice among prominent speakers. But we are also aware of the obligation we hold to be respectful of our host community. The emotional scars of the murder of Boston Police Sergeant Walter Schroeder, allegedly at the hands of the Weather Underground, which left nine children fatherless in the shadows of this campus, was an issue that we could not ignore."
So the college called off the event, the statement said, "out of respect for the Schroeder family and out of concern for the safety and well being of our students. We believe that, in light of these unique circumstances, the appropriate decision was made in this case."
Boston College students are now trying to find a site off campus for Ayers to speak tonight.
In an e-mail to Inside Higher Ed, Ayers condemned the college's decision to bar him from appearing on campus. "My involvement in the Weather Underground in the 1970s is well known and entirely public, and all legal issues were dealt with decades ago," he said.
Of Boston College's statement, he said: "The killing of the police officer they refer to resulted in several arrests and convictions, and the Weather Underground had nothing to do with it. There has to be more to the BC decision. The BC statement is outrageous, dishonest and indefensible."
Melissa Roberts, a senior at Boston College who was among those organizing the event, said she was bothered by several issues. First, she noted that there is no evidence that Ayers was "in any way involved" in the 1970 killing, so she wondered why a college should be taking actions based on "some people thinking that he was involved, when he wasn't."
Second, she noted that students had worked with administrators for "weeks and weeks" on the event, only to be told at the last minute that it would be called off.
And third, she noted that Boston College students must already accept some limits on the speakers they can bring to campus if they are likely to express views that conflict with Roman Catholic teachings. Now, she said, the college is going further. "If they can cancel any event that goes against the whims of wealthy conservative donors, that's very concerning to me. That's not academic freedom."
Ayers has been on the college lecture circuit for years, and before the McCain campaign last year tried to link him to Barack Obama, most of those appearances were uneventful. Since the campaign, Ayers's appearances have attracted protests, but have generally gone on as planned. But the University of Nebraska at Lincoln  and Georgia Southern University  have uninvited Ayers, citing security issues.
Cary Nelson, national president of the American Association of University Professors, said that he is worried about the implications of Ayers events being called off.
"Every Bill Ayers speech has now become a national test case for academic freedom. He is a distinguished professor of education with a past. But no one is really exercised about the Weather Underground any more," he said. "A protest about an Ayers speech is an opportunity to assert external power over campus intellectual life. You call up with an anonymous threat, and a college or university president gets to make solemn noises about security. The threatening phone call is now the ultimate heckler's veto. Every time a campus succumbs to one intellectual integrity is diminished for all of us."