The Legion doesn't have any citizens as Sawyer has stated.
"Though Caesar keeps Primm open for business, its citizens live under the constant watch of Legion soldiers"
- Ending of Fallout New Vegas (Primm Slide when you make NCR control it)
The Legion doesn't currently have citizens before Hoover Dam. But they change when they get Vegas because it's a good, triumphant symbol of Caesar's power. Or something along those lines. That's essentially what makes Caesar's Legion not a generic evil faction of slavers like in Fallout 3.
They have the organization, the background ideological values (Hegelian Dialectics, Utilitarianism, etc.), and the future success.
The problem with this being 200 years after the bombs drop is no longer living in the remains of a nuclear holocaust as groups like the NCR with railroads and factories demonstrate. If Caesar was making his argument before we'd seen humanity come back from the brink he'd have a stronger case.
That's true. But Caesar's point is that NCR is making people weak and NCR is breaking apart. Whether or not he has a good case for NCR breaking apart is irrelevant: Corruption. That's another one of Caesar's points and he's right.
Both Caesar and House have zero personal corruption as far as we've seen and keep corruption of their lackeys in check. But in NCR, Kimball and Oliver are the ones doing the corruption while people like Moore who fanatically support Oliver's regime are awarded while smart people like Hsu aren't. Or even smarter people like Hanlon have to resort to breaking the law to get their message across.
In Caesar's case, it's a moral, societal thing. That's why the Legionaries call everyone who's not them a dissolute, one lacking in morals but can be redeemed by assimilation. Whether or not they're right or wrong, it's their ideology and their theme in the New Vegas storyline.