OK, I've only read the first three books of Plato's Republic, but I'm not one to let that dissuade me from an opinion. The tone of the Republic seems much different than the dialogs, possibly indicating that Plato is no longer attempting to recreate Socrates, but express his own thoughts, even though he still attributes them to Socrates. The Socrates of the Republic is far more didactic, declaiming his ideas and mostly winning the equivalent of "Well duh" from his interlocutors.
I suppose we can credit Plato with the invention of the totalitarian state, at least as an intellectual concept. He argues that by systematic thought control, a few well chosen big lies, and a bit of selective pruning of the unsuitable, the ideal governors and guardians of the state can be educated and entrusted with its governance.
My reaction was that this represents a woeful misreading of human nature, but one that continues to be made pretty widely even in our day - what Steven Pinker calls the "blank slate" fallacy.
Among other dumb ideas, he thinks that each person should only be permitted to do the things that he is best at.
SOCRATES: Well, now, we prevented a shoemaker from trying to be a farmer, weaver, or builder at the same time, instead of just a shoemaker, in order to ensure that the shoemaker’s job was done well. Similarly, we also assigned just the one job for which he had a natural aptitude to each of the other people, and said that he was to work at it his whole life, free from having to do any of the other jobs, so as not to miss the opportune [c] moments for performing it well. But isn’t it of the greatest importance that warfare be carried out well? Or is fighting a war so easy that a farmer, a shoemaker, or any other artisan can be a soldier at the same time, even though no one can become so much as a good checkers player or dice player if he considers it only as a sideline and does not practice it from childhood? Can someone just pick up a shield, or any other weapon or instrument of war and immediately become a competent fighter in an [d] infantry battle or whatever other sort of battle it may be, even though no other tool makes someone who picks it up a craftsman or an athlete, or is even of any service to him unless he has acquired knowledge of it and has had sufficient practice?
Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 265). Hackett Publishing Company, Inc.. Kindle Edition.