O'Reilly's comments are protected by the U.S. Supreme Court's decision in Brandenburg vs. Ohio, the San Francisco Chronicle said. On June 9, 1969, the court ruled that a Ku Klux Klan member, Clarence Brandenburg, had a right to talk about "revengeance" if government institutions continued to oppose the white race.
"Mr. O'Reilly has a constitutional right to be an obnoxious bloviator," David Hudson, a lawyer with the First Amendment Center in Nashville, told the newspaper.
Tiller -- who ran an abortion clinic in Wichita and was one of the few doctors in the country willing to perform third-trimester abortions -- had been a target of violence and vandalism for years, along with harsh words from O'Reilly and others. O'Reilly often noted that some of Tiller's critics called him "Tiller the baby-killer" -- and O'Reilly himself occasionally used the term.
After Tiller was killed while attending church May 31, O'Reilly said that kind of violence was wrong, CNN reported. But he also expressed concern about how reaction to the slaying might affect his show on Fox News.
"When I heard about Tiller's murder I knew pro-abortion zealots and Fox News haters would attempt to blame us for the crime," O'Reilly said. "Every single thing we said about Tiller was true."