Now, Adeimantus comes in to emphasize that it is the consequences of justice (not justice itself) that are praised, both by the gods and the poets and teachers. What the poets show is that justice is for the weak, not the clever and strong who can get everything they want. Moreover, he throws in a twist: he doesn’t want arguments; he wants to be shown! Adeimantus is skeptical of arguments, he distrusts them. The question, then, is: how do you convince someone of something without argument, when someone is skeptical of speech? Socrates’s answer is an experiment in thought: to found the city in speech.
The founding of the city in speech is an attempt to address a perennial political problem: how do you educate the young, ambitious youths who are distrustful of speeches and who have conventional views of justice and philosophy? It is not accidental that from here on out the dialogue is overwhelmingly concerned with the education of the ruling class, that is, with those who give character to the regime.
If you need proof that the ruling class gives a regime its character, simply look at our own.