One trouble with pretending to be someone or something else is that there is no stopping it. For Plato, the act of pretending rapidly runs down through a sexist chain of being from men to women to animals to inanimate objects, in a crescendo of degradation. Socrates’s affirmation of this terrible danger in poetry is the classic condemnation of imitation in the Western tradition. Imitation is a species of dehumanizing or unmanning (!) madness. Poetry, for Plato, has authority all right, but it is the authority of radical evil. Therefore the poets must be banished from his ideal republic.
I don't know in this context classic mean: traditional or typical or admired?
This passage is from a book named: On literature.