Paul:
Leto remembers much further back than Greco-Roman times
et cetera. I know, the pharaonic model refers to pharaohs. These, and the length of Leto's memory, are minor details; the importance is the pervasiveness of the model of government.
Inquisitor:
Leto was saying that is was the wholesale passing on of responsibility to the leader, not their deification; the leader is expected to tell people not only how to help with the grand social vision, but also how to behave, how to feel... Leto's complaint about the system was that each person looked up to him (or some other leader, in other times) to tell them how to be, instead of deciding for themselves as some kind of collective, or some other system like that...
The idea was that the citizen turned over their civil responsibility to intelligence by giving all such responsibilities to the leader instead.
If the President of the US decided to take an action that blew up in his face in a predictable way, what would the citizens of the US do? Would they say, "We were wrong to support the President in such an obviously foolish action?" Nah, they'd say, "We need a new President. This one sucks."
All civil responsibility is therefore invested in the leader, because when the country's actions go wrong, its citizens claim that it's the fault of the leader that they appointed. "Beyond the choice of a representative," they say, "we don't want to understand anything about what our country does." That way, when things go wrong, they can protect themselves with claims of ignorance and helplessness.
What's wrong with this model? Leto demonstrates.
Imagine if the giant worm is the President of the US.
He gets up today on the TV, and says,
"Inquisitor (that's you) has been investigated and found to be corrupt and utterly lacking in moral fibre. He (or she) is an example of the most hideous failure of our inability to foster human goodness in the pathetic and wasted shells of people like him (or her). As such, his house will be bombed into ashes at 9:48 this morning, Eastern Standard Time. Bless you all, except for Inquisitor. Good morning."
You check your watch, and it's 9:48. So, what're you gonna do, vote? You gave up your civil responsibilities in the last election (assuming you ever had a chance to exercise them at all) to a giant worm who's about to kill you. And the best part is, you gave away that civil responsibility to him whether you voted for him or not. All you can really do now is have them carve "This President sucks. We need a new one," on your tombstone.
That's the point. Leto is trying to break people's dependence on this kind of leader, by pissing them off so bad that they don't want him, and ensuring that there's no one else who could even come close to replacing him.