What is the psychology behind a witch hunt?

[hanson f]

What is the benefit of labeling an investigation on you as a witch hunt?

[GIO C]

To warn the people against the Devil

[siddhartha]

Turning public anger and frustration back against the old folk devils of witchcraft
until a general hysteria takes over and all else is blamed upon the witches who
we are told must be burned to rid society of its ills. Meanwhile corruption continues
unabated and unchecked to the profit of the witch-hunters!

[tuffy]

The psychology behind calling an investigation a "witch hunt" is to insinuate that the investigation has no hard evidence about the people being investigated, but if one throws out charges against everyone any guilty person(s) might be identified. For example, if someone is accused of being guilty of something and he/she is not guilty, it can ruin his/her reputation. This happened in the U.S. during the McCarthy era (1950-1954) especially in Hollywood against writers, directors, and actors who were guilty of nothing, but could not find work for years.

[staisil]

A witch-hunt is a search for suspected witches; it is a type of moral panic.

A moral panic is a mass movement based on the perception that some individual or group, frequently a minority group or a subculture, is dangerously deviant and poses a menace to society. These panics are generally fuelled by media coverage of social issues (although semi-spontaneous moral panics do occur), and often include a large element of mass hysteria.