"Almost everyone agrees with me, so I must be right"
If you suggest too strongly that someone’s claim or argument is correct simply because it’s what most everyone believes, then you’ve committed the fallacy of appeal to the people. Similarly, if you suggest too strongly that someone’s claim or argument is mistaken simply because it’s not what most everyone believes, then you’ve also committed the fallacy. Agreement with popular opinion is not necessarily a reliable sign of truth, and deviation from popular opinion is not necessarily a reliable sign of error, but if you assume it is and do so with enthusiasm, then you’re guilty of committing this fallacy. It is essentially the same as the fallacies of ad numerum, appeal to the gallery, appeal to the masses, argument from popularity, argumentum ad populum, common practice, mob appeal, past practice, peer pressure, traditional wisdom.
(source: internet encylopedia of philosophyhttp://www.iep.utm.edu/fallacy/#Appeal%20to%20the%20People)
See also: begging the question, Annihilationism is unorthodox because only unorthodox christians believe in annihilationism.