Because clearly New Vegas is such a wonderful place, filled with junkies, thieves, whores and gangsters.
Funny cuz' that kind of moralizing BS is also what led to the Great War...
OK, you got me there...
But still, what I meant to say is, NCR represents in my opinion everything that is both good and bad with the old world. Unfortunately, the result is often those bad things winning.
In Fallout universe, I think, the NCR portrays how "resurrectionists", while their intentions may be good, can unintentionaly bring back some of the worst things about society they're fighting to preserve. They resurrect it with all those flaws that led to the Great War, although that may not be their intention.
But the problem is, the old world is gone in the Fallout universe. So you can't exactly cling onto it's ideals and social norms. NCR wants to bring back democracy? Great, but they're not living in a world before the bombs where that was possible. There were no giant scorpions and drugged up Fiends back then. There was infrastructure, education system (a BIG deal in Fallout universe, the one nobody ever talks about), security, and a significantly smaller number of people that wanted (or wanted, but COULDN'T) put a bullet in your head because they felt like it.
Democracy is useless at this point in their history, at least for the time being. They have far bigger problems that need to be dealt with - by iron fist, not clean elections and freedom of speech for everyone.
The Legion, on the other hand, offers an alternative.They have zero tolerance for criminals of any kind. They want to bring order to a savage wasteland, and they have the muscle to do it. Their methodes are crude, and there is excess, sure, but that's the case with every revolution. You can't exactly sit down and have a diplomatic talk with an uneducated violent raider that carved up a women today because he wanted to steal her water. If you want to keep those kinds of people in line, you need a strong arm. In those extreme conditions, you need to keep things simple for everyone. And even the dumbest thug understands what a punch in the face means. You can't defeat a bully ba letting him voice his opinions and getting him to talk about his feelings. You need to be bigger, stronger, meaner and crazier.
The Caesar may be a guy with a vision, but in order to turn that vision into reality, he needs quick results. Direct approach is the only way in that case. Bureaucratic BS, corruption, and a bunch of ignorant people protesting left and right because they're "entitled" to their opinion about everything would undermine his cause. Old world morals and democratic ideas would simply be counter-productive.
Do I support everything a Legion does? No. Do I think it needs to change? Yes, and it inevitably will, just like every society changes after the war ends. If I were Caesar, would I do some things differently? Absolutely. But let's not forget that we mostly just hear about Legion's alleged atrocities from some third party who may or may not have actually witnessed it. Who knows how much of that is propaganda?
Now some people will say "But what about Nipton?". Nipton? You mean the town that was in cohoots with Powder Gangers, a bunch of escaped criminals that terrorized every town nearby? A gang of ruffians that you spent a healthy portion of the game butchering? Whose mayor tried to sell both the NCR soldiers and his alleged allies, even his own PEOPLE, to the Legion? Yea, I'd say the Legion actually showed restraint when punishing that scum...
But do they deserve such hatred? No. I know a lot of content had to be cut from the game, and that every video game needs a good villain, and Legion seems to fit that role perfectly.
All I'm trying to do is look at things from their perspective. Their methodes may be cruel, but I think they do have a solid reason for acting the way they are. Maybe a DLC will come out that will focus on their side of the story. That would be amazing!