There are at least two more issues worth commentary in this book. The second of those two is the regulation of drinking, about which the concluding remarks are concerned. You end up with something like Prohibition except for mandatory social drinking for approved ends. That's sort of the worst of both worlds, there.
The first is a kind of artistic censorship.
Ath. [I]f I were a lawgiver, I would try to make the poets and all the citizens speak in this strain, and I would inflict the heaviest penalties on any one in all the land who should dare to say that there are bad men who lead pleasant lives, or that the profitable and gainful is one thing, and the just another... For tell me, my good friends, by Zeus and Apollo tell me, if I were to ask these same Gods who were your legislators-Is not the most just life also the pleasantest? or are there two lives, one of which is the justest and the other the pleasantest?-and they were to reply that there are two; and thereupon I proceeded to ask, (that would be the right way of pursuing the enquiry), Which are the happier-those who lead the justest, or those who lead the pleasantest life? and they replied, Those who lead the pleasantest-that would be a very strange answer, which I should not like to put into the mouth of the Gods.
There's a great deal more by way of argument about why this is philosophically correct. I'm going to stick to a different question, which is whether it is or is not good art -- good both in the sense of making interesting art, art that is true to the world, and also in the sense of whether it does in fact improve people to have art of this sort primarily presented to them.
So, one way to approach this topic is by telling the story of Conan the Barbarian.
Conan is well-familiar to readers of this page, but mostly as he was in his original incarnation: the works of Robert E. Howard. Sometime after Howard's death in 1936, the Conan intellectual property was picked up by L. Sprague De Camp. De Camp's role in the story of Conan is much debated, but one thing that is clear about it is that De Camp decided to purify Conan of some of Howard's wilder aspects.
He was influential on Conan's second life as a comic book character, which was constrained by a set of moral codes governing comic books at that time. They were close to the ones Plato is recommending here: that a protagonist should be just, not merely successful. The Conan that is produced by this careful censorship is much like the hero of the detective noir that Raymond Chandler promised in 1950:
"But down these mean streets a man must go who is not himself mean, who is neither tarnished nor afraid. The detective in this kind of story must be such a man. He is the hero, he is everything. He must be a complete man and a common man and yet an unusual man. He must be, to use a rather weathered phrase, a man of honor, by instinct, by inevitability, without thought of it, and certainly without saying it. He must be the best man in his world and a good enough man for any world. I do not care much about his private life; he is neither a eunuch nor a satyr; I think he might seduce a duchess and I am quite sure he would not spoil a virgin; if he is a man of honor in one thing, he is that in all things."
That figure is also the hero of Louis L'amour novels. He could wear Chandler's trenchcoat and fedora, L'amour's Stetson and duster, or Conan's wolf-cloak and sword -- but he is not Conan.
I have written approvingly before of L'amour's effect on moral education. I definitely think that, if the stories are being written for moral education, there's a lot to be said for this approach. And all three of these sets of stories -- Chandler's, L'amour's, and the Conan stories -- have also been highly successful as art. People consume these things across generations, not as matters of fashion but out of recognition of a deep truth about the world.
Yet Conan as Howard wrote him is not a man like this, and it was violence to his character to try to distort him into another token of the type. Conan is just as happy to be a pirate as a hero, and perhaps happier. In the famous adventure with Belit, he watches her and her crew kill all of the proto-Greek sailors he had shipped with but chooses to side with her for perfectly lustful reasons. He then becomes her right hand at piracy, and describes himself as highly satisfied:
Let me live deep while I live; let me know the rich juices of red meat and stinging wine on my palate, the hot embrace of white arms, the mad exultation of battle when the blue blades flame and crimson, and I am content. Let teachers and priests and philosophers brood over questions of reality and illusion. I know this: if life is illusion, then I am no less an illusion, and being thus, the illusion is real to me. I live, I burn with life, I love, I slay, and am content.
Conan is described by Howard not as a 'man of honor,' though he has a 'rude chivalry' and treats women invariably with kindness -- sometimes respect. But he is a red-handed killer, and loves his pirate queen and the life she gives him.
Conan is a hero, though, like Achilles is a hero, like Odysseus is. Homer is Plato's foe here, and Homer may be greater than Plato. The fire Homer captures must have something of the divine in it, and yet it is that very quality that Plato wishes to tamp and tame. Plato has reasons to try to tame that divine fire; yet if it produces such men as Conan and Odysseus, how can we say it is wrong?