“When Palin and others describe Obama as professorial in style, they are invoking themes and tropes that have a long history in American politics,” says Neil Gross, an associate professor of sociology at the University of British Columbia. “That longstanding tendency in American politics is also in this case being drawn together with an implicit criticism of liberal professors, which really only became a mainstay of conservative discourse in the 1950s.”
A leading voice in that discourse was the late William F. Buckley Jr., who famously opined that he’d “rather entrust the government of the United States to the first 400 people listed in the Boston telephone directory than to the faculty of Harvard University.” Other conservatives took aim at Harvard faculty as well, including Richard Nixon, who derided that pesky special prosecutor, Archibald Cox, as a “fucking Harvard professor,” according to Bob Woodward and Carl Bernstein’s account in The Final Days.
The use of “professor” as a term of derision may have hit its stride in the 1950s, but it dates back to scolding characterizations of Socrates, according to Geoffrey Nunberg, a linguistics professor at the University of California at Berkeley. By the 1940s, Hollywood had cashed in on the stereotype with a film called “Ball of Fire,” which cast Gary Cooper against type as a naïve professor who learns the real ways of the world from a nightclub dancer called Sugarpuss O'Shea. In the political realm, Adlai Stevenson was similarly labeled an “egghead” in his 1950s campaigns for the presidency, Nunberg added.
If the term professor is used in politics, it's seldom a compliment, and instead "implies dry, hectoring, unemotional, self important, all of the negative stereotypes of somebody who is vainly certain of his own superior mental capacities but doesn’t have a human connection,” says Nunberg, author of The Years of Talking Dangerously and a frequent contributor to NPR’s “Fresh Air.”
That's from this Inside Higher Ed article by Jack Stripling.