As a literal parade

"Parade of horribles" originally referred to a literal parade of people wearing comic and grotesque costumes, rather like the Philadelphia

Philadelphia, Pennsylvania

Philadelphia is the largest city in the Commonwealth of Pennsylvania and the county seat of Philadelphia County, with which it is coterminous. The city is located in the Northeastern United States along the Delaware and Schuylkill rivers. It is the fifth-most-populous city in the United States,...

 Mummers Parade

Mummers Parade

The Mummers Parade is held each New Year's Day in Philadelphia, Pennsylvania. Local clubs compete in one of four categories . They prepare elaborate costumes and moveable scenery, which take months to complete...

. It was a traditional feature of Fourth of July parades in parts of the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in the nineteenth century, and "Horribles Parades" continue to be part of the Independence Day celebration in several New England

New England

New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...

 communities. A 1926 newspaper article about July the Fourth celebrations in the White Mountains

White Mountains (New Hampshire)

The White Mountains are a mountain range covering about a quarter of the state of New Hampshire and a small portion of western Maine in the United States. Part of the Appalachian Mountains, they are considered the most rugged mountains in New England...

 of New Hampshire

New Hampshire

New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

 notes:

Old-time celebrations are to be held tomorrow at Littleton

Littleton, New Hampshire

Littleton is a town in Grafton County, New Hampshire, United States. The population was 5,928 at the 2010 census. Situated at the edge of the White Mountains, Littleton is bounded on the northwest by the Connecticut River....

, Lancaster

Lancaster, New Hampshire

Lancaster is a town in Coos County, New Hampshire, USA, on the Connecticut River named after Lancaster, England. As of the 2010 census, the town population was 3,507, the second largest in the county after Berlin. It is the county seat of Coos County and gateway to the Great North Woods Region...

, Colebrook

Colebrook, New Hampshire

Colebrook is a town in Coos County, New Hampshire, United States. The population was 2,301 at the 2010 census. Situated in the Great North Woods Region, it is bounded on the west by the Connecticut River and home to Beaver Brook Falls Natural Area....

, and Conway

Conway, New Hampshire

Conway is a town, the largest in Carroll County, New Hampshire, United States. The population was 10,115 at the 2010 census. Parts of the White Mountain National Forest are in the west and north. Cathedral Ledge and Echo Lake State Park are in the west...

, with all the usual features of street parades of horribles and grotesques, brass bands, decorated automobiles and vehicles, exhibitions by fire departments, basket picnics in convenient groves...

Founded in 1926, the Ancient and Horribles Parade

Ancient and Horribles Parade

Ancient and Horribles Parade, founded in 1927, is a nationally known Fourth of July parade on U.S. Route 44 in the village of Chepachet, Rhode Island in the town of Glocester...

 in Chepachet, Rhode Island

Chepachet, Rhode Island

Chepachet is a village and census-designated place in the town of Glocester in the northwestern part of the U.S. state of Rhode Island. It is centered at the intersection of U.S. Route 44 and RI Route 102...

 continues this tradition.

As a rhetorical device

A parade of horribles is also a rhetorical device

Rhetorical device

In rhetoric, a rhetorical device or resource of language is a technique that an author or speaker uses to convey to the listener or reader a meaning with the goal of persuading him or her towards considering a topic from a different perspective. While rhetorical devices may be used to evoke an...

 whereby the speaker argues against taking a certain course of action by listing a number of extremely undesirable events which will ostensibly result from the action. Its power lies in the emotional impact of the unpleasant predictions; however, a parade of horribles can potentially be a logical fallacy if one or more of the following is true:

• The action doesn't actually change the likelihood of the "horribles" occurring. The "horribles" could be unlikely to occur even if the action is taken, or they could be likely to happen anyway even if the action is avoided. This is an appeal to probability
  Appeal to probability
  An appeal to probability is a justification based on probability, sometimes regarded as a logical fallacy, when an unwarranted assumption that something will happen, because it can happen, or when the odds of an occurrence are unrealistically played down in lieu of appropriate precaution.Although a...
  
  , and can be viewed as a non sequitur (logic)
  Non sequitur (logic)
  Non sequitur , in formal logic, is an argument in which its conclusion does not follow from its premises. In a non sequitur, the conclusion could be either true or false, but the argument is fallacious because there is a disconnection between the premise and the conclusion. All formal fallacies...
  
   insofar as the action has no causal relation to the "horribles".
• The argument relies solely on the emotional impact of the "horribles" (an appeal to emotion
  Appeal to emotion
  Appeal to emotion is a potential fallacy which uses the manipulation of the recipient's emotions, rather than valid logic, to win an argument. The appeal to emotion fallacy uses emotions as the basis of an argument's position without factual evidence that logically supports the major ideas endorsed...
  
  ).
• The "horribles" are not actually bad.

A parade of horribles is a type of hyperbole

Hyperbole

Hyperbole is the use of exaggeration as a rhetorical device or figure of speech. It may be used to evoke strong feelings or to create a strong impression, but is not meant to be taken literally....

, because it exaggerates the negative results of the action, arguing that "If we do this, ultimately all these horrible things will happen".