Frankly, claiming that Plato is fascist is pure nonsense. It's ignoring the history of political thought (including, notably, Plato) and the economical and societal background that led to fascism.

You can argue that he inspired fascism or that he was a kind of proto-fascist. That would be weird (since it would exclude all the modern causes and influences for fascism), but arguable. But calling him a fascist is just an anachronism.