CARBONDALE, Ill. -- Questions of academic freedom are simmering at Southern Illinois University after history professors criticized a colleague over his use of an article about black-on-white killings in San Francisco in the 1970s.

History professor Jonathan Bean, a self-proclaimed "libertarian conservative," claims he is the victim of public attacks by a history department filled with professors who hold political views opposite his.

His colleagues say they fault him for distributing to students what they call a "distorted and inaccurate" account of the so-called "Zebra" killings, a series of random street slayings of whites in San Francisco in the early 1970s.

Bean said he assigned the article in April as optional reading material to students in his American history class.

"It was simply to give them a chance to learn about something they may have never heard about," Bean said.

He canceled the assignment a few days later, though, after history department chairwoman Marjorie Morgan told him the article was inflammatory and insensitive, Bean said.

Bean said he has received a letter from the dean of the College of Liberal Arts, Shirley Clay Scott, saying she considers the matter closed.