David Horowitz was hit in the face with a pie Wednesday during a speech at Butler University. The attack was the third incident in the last 10 days in which a conservative speaker has been doused with food while trying to speak on a Midwestern campus.

William Kristol, editor of the Weekly Standard, was hit in the face with a pie during a speech at Earlham College and Pat Buchanan, the former presidential candidate, had salad dressing thrown on him at Western Michigan University.

Horowitz was at Butler as part of his campaign to encourage state legislatures to adopt the "Academic Bill of Rights," which Horowitz says will encourage a diversity of views in higher education, but that critics say is an attack on academic freedom. In a statement on the incident at Butler, Horowitz said, "It is ironic that these assailants tried to prevent me from delivering a lecture on the need for greater tolerance and respect for dissenting opinions in the academic community."

After the incident, Horowitz finished his speech.

A spokeswoman for Butler said Thursday evening that officials were investigating the incident and that the pie-thrower had not been identified.

Bobby Fong, president of Butler, called Horowitz to express his concern and issued a statement Thursday criticizing the attack.

"A university is at its best a forum for the open exchange of ideas and opinions. Mr. Horowitz's right to express his opinions was violated by those who disrupted his speech," the statement said. "We support the constitutional rights of free speech granted to Mr. Horowitz as well as to those who disagree with his opinions. The university does not support this inappropriate behavior."

In the attack on Pat Buchanan, the assailant was identified by authorities as a student at Kalamazoo Valley Community College.

Earlham College suspended the student who threw a pie at Kristol. Earlham issued a statement Thursday affirming the importance of letting speakers address their audiences. The statement said that "any student who shows by word or deed that he or she will act to deny such rights to speakers and their potential audiences will forfeit the privilege of continuing to be a student at the college."

In explaining the reason for issuing the statement, the college said: "The exercise of speech is a fundamental principle upon which we organize this college and is essential to any college or university worthy of the name. That principle must be a visible and undoubted commitment of the college at all times. When it is threatened, the college must take steps to reaffirm that commitment."