Professor Richard Berthold will also get a letter of reprimand and undergo review, said Brian L. Foster, university provost.
The 55-year-old tenured professor told a freshman history class just after the attacks that "anyone who can blow up the Pentagon has my vote."
Berthold has apologized for his comment, which he called "an incredibly stupid joke." He did not immediately return a phone call Monday.
Berthold stayed off campus for a brief period while police investigated obscene and threatening calls to the history department. He also said he was assaulted in front of his home.
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