tactical facepalm (tak-ti-kuhl feys-pahm)
1. A maneuver performed by a unit of Internet denizens in response to an overwhelming onslaught of ignorance. The maneuver involves each member of the unit performing a standard facepalm in unison. Executed properly, the tactical facepalm is the only known defense against spontaneous cerebrofulmination—also known as "exploding head syndrome" (EHS)—resulting from exposure to extreme stupidity.
Earnest idiot: Africans were wholly responsible for slavery in the European world. Whites only bought what African slavers were offering. They're completely innocent!
Forum dweller CO: Squad, initiate tactical facepalm!
Forum dwellers: Sir, yes, sir! *facepalm*
Forum dweller XO: EHS averted, sir!