Appeal to the Majority

This is also called Popular Appeal and Argumentum ad populum.

Examples

• The majority once believed that smoking is healthy and good.
• The majority in some countries believe in the existence an invisible man in the sky despite an utter lack of evidence.
• The majority once believed that the world was flat.
• The majority once believed that the world was the center of the universe (until conspiracy theorist Galileo Galilei insisted otherwise).
• The majority once believed that DDT was safe and beneficial.
• The majority frequently mistakes economic bubbles for genuine prosperity.

Weaknessess

Appeal to the Majority asserts that somehow the crowd knows what is right and true. History is littered with examples of the contrary, because crowds are easily riled up, deceived, comprised of blind followers, and made to become irrational.

The collective IQ of a group is often lower than that of the individuals in the group.

When refuting Argumentum ad populum, draw on your understanding of groupthink, which is the phenomenon in which a group's collective decision-making is poor because members are afraid to speak up or rock the boat. Groupthink can operate on a societal scale, as you see in dictatorships. In Medieval Japan, the motto was: The nail that sticks up gets hammered down.

You can interrogate your opponent on the exact mechanism by which the majority ascertains the truth better than the individual does.

You might mention how people are notoriously bad at determining the truth value of rumors, and how when they spread they become more fantastical and less based on fact.

Difference between perceptions and opinions

The perceptions of a set of people are a different matter from their interpretations or opinions. Perceptions are useful and valuable when they are independent, honestly conveyed, and fresh, since they are are data points -- evidence -- from which truth can be ascertained by inductive reasoning.

Quotations

Whenever you find yourself on the side of the majority, it is time to reform.

Mark Twain

The public will believe anything, so long as it is not founded on the truth.

Edith Sitwell

The majority seeks power, status, and wealth, and not truth.

Plato

You, the people, are a many-headed beast.

Horace (Epistles)