From Wikipedia: Academia is sometimes contrasted pejoratively with "practice", such as daily living, employment, and business. Critics of academia say that academic theory is insulated from the 'real world', and thus does not have to take into account the real effects, results, and risks of actually performing the actions which academics study. Academic insularity is sometimes referred to as the ivory tower.
From Dictionary.com, one definition of "academic": theoretical or hypothetical; not practical, realistic, or directly useful: an academic question; an academic discussion of a matter already decided.
Again from Wikipedia: In political jargon, the term useful idiot was used to describe Soviet sympathizers in Western countries and the attitude of the Soviet government towards them. The implication was that though the person in question naïvely thought themselves an ally of the Soviets or other Communists, they were actually held in contempt by them, and were being cynically used.
The term is now used more broadly to describe someone who is perceived to be manipulated by a political movement, terrorist group, hostile government, or business, whether or not the group is Communist in nature.
Professors are people who tell us how to solve the problems of the world; problems they themselves avoided by becoming professors.