It is a popular fallacy that all man-eaters are old and mangy.

Observation : the action or process of closely observing or monitoring something or someone.
Belief : an acceptance that something exists or is true, especially one without proof.
Fact : a thing that is known or proved to be true.
Illusion : an instance of a wrong or misinterpreted perception of a sensory experience.
Fallacy : a mistaken belief, especially one based on unsound arguments.

Synonym of Fallacy is Belief