jeerleader
n. A person who leads the jeering of spectators; a person who expresses thoughtless disapproval of another person or thing.

Example Citation:
"Sometimes I read Clinton-bashing columns or Letters to the Editor just to witness how petty hatred can be. A good source is George Will—chief jeerleader on the Forum Page—who doubles the nation's stockpiles of irony every time he calls someone other than himself arrogant."
—Stephen Hiltner, "Critics refuse to give Clinton credit," The Herald-Sun (Durham, N.C.)

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