Fallacy

That's not a valid argument. It's a logical fallacy.

The fact that most criminals belong to a certain group does not imply that most members of that group are criminals. To claim that it does is to commit the inverse fallacy.

Let me therefore enter upon this noble cause with a chearfulness, grounded upon this assurance, that my adversary's cause is maintain'd by nothing but fraud, fallacy, ignorance and barbarity; whereas mine has light, truth, reason, the practice and the learning of the best ages of the world, of its side.

This is a fallacy.

If a hotelier touts an unproven or dangerous medicine, or if a film actor sells polished stones or scented candles with purported health benefits, these are examples of a kind of informal fallacy called an "appeal to authority".

Although an appeal to popularity is in fact a logical fallacy, a religious person may sometimes speak of an ecumenical truth as being right or true because everyone believes it.

Finishing a book or movie you've started but don't like is a good example of the sunk cost fallacy.

Affirming the consequent is an example of a formal logical fallacy.

Those rumors are a fallacy.

Stating that Berber dialects are separate languages is a common fallacy upheld by Western linguists who have little knowledge about the linguistic reality of North Africa. Mutual intelligibility among Berber speakers, particularly those who speak Northern Berber dialects is a verifiable fact.