His concrete solutions are to choose representative democracy over direct democracy, and to have large republic rather than a small republic.

Why? How does this fix things? Without quite knowing what problem this solution is meant to address, the first consequence of this policy (representative democracy + large republic) that comes to my mind by judging it independently is that it looks optimized for the smallest number of rulers and the greatest amount of people limited in their political power by comparison -- in other words, it seems to concentrate power. (If there are other implications, they're not as obvious to me as this one.) How or why does that help overall impartiality?