Argumentum ad populum

From Conservapedia

Argumentum ad populum (appeal to the people) is a logical fallacy that concludes that a position is true because many or all people believe it. i.e: "If many believe so, it is so." Other names for this are appeal to the masses, appeal to belief, appeal to the majority, appeal to the people, argument by consensus, authority of the many, bandwagon fallacy, and tyranny of the majority.