Bandwagon fallacy
The bandwagon fallacy, also known as appeal to the people, authority of the many, argument by consensus, appeal to the gallery, appeal to popularity or argumentum ad populum, is a fallacy where something is 'proven' by stating that many or all people believe it.For example, one could claim that smoking is a healthy pastime, since millions of people do it. However, knowing the dangers of smoking, we instead say that smoking is not a healthy pastime despite the fact that millions do it.
Of course, this only applies to 'something' with an objective criteria, such as the health effects of smoking. In areas of a subjective nature, such as fashion or music, it could be argued that the "authority of the many" or the "appeal to popularity" is a true reflection of the subjective desires of a population group.
While the argument may seem convincing when not examined, a simple refutation would lie in pointing out that at a time not too distant in United States history, it was common to hold other people as slaves, which few people today would consider ethical.
The bandwagon fallacy is a pillar of advertising, along with the appeal to authority fallacy. It is a red herring and genetic fallacy.