The spinless Mob...

...The term is borrowed from ornithology. Every so often birds in a flock will turn, as one, on a perceived threat (either outside, or inside their group) and harass some luckless victim into flight or exile. It often seems less a response to genuine danger, than a reflexive action making for collective cohesion ("we're all in this together - except that bastard over there. Let's get him"). The application of this avian behaviour to workplace situations was first made by a German social psychologist, Heinz Leymann, in the 1980s. Dr Leymann defined human mobbing as "an impassioned, collective campaign by co-workers to exclude, punish, and humiliate a targeted worker" - usually without appropriate cause...

From: Not strictly for the birds

...In 'On Aggression' (1966), Konrad Lorenz (1903-1989), the Austrian-German founder of ethology, described mobbing among birds and animals, attributing it to instincts rooted in the Darwinian struggle to survive. In his view, we humans are subject to similar innate impulses but capable of bringing them under rational control. He jointly won the Nobel Prize for Physiology/Medicine in 1973...

From: Workplace Mobbing in Academe