Let's take some inspiration from some other genres, and look at this LG tyranny based on it's agenda.
So let's say the PCs are in the conventional 4e points of light style setting. It's a rough world, mostly in ruins, and the threat of evil and chaos is ever-present. There are few if any kingdoms remaining, and heroes are needed to fight hard if they're going to save the world.
Some distance from where the PCs reside, is a small kingdom known for it's safety and virtue. An order of knights from this kingdom run chapter houses in the area, and hire the PCs for various missions.
They pay them very well, and offer them magical items, ritual components, ect, both for sale and as rewards. They work with this order for some time, hunting down cultists, slaying orcish and gnoll chieftains, exploring and recovering ancient artifacts, and defending other smaller comunities in their own area. The PCs are often aided by prophecies or auguries presented to them by the knights, who claim they come from seers back home.
Then the PCs get to paragon tier or whatever, eitehr wya they take a trip to the kingdom who's knights have supported themf or so long. And they find out where all those cash rewards and magical items were coming from.
The entire kingdom is set up as a militaristic theocracy. It has to be, so the knights claim, in order to defend its borders, and beat back the tide of evil and chaos in the world. If the world is ever to recover- or just go on surviving- then the Kingdom must be not just a bastion or a beacon, but a well-oiled and effective fighting machine. It's armies are not large enough to tame the endless hordes of orcs and the like, so it's splits it's efforts between conventional military forces, and more powerful agents- like the PCs.
Most people in the kingdom are serfs- they have to be, somebody has to grow the food, mine the metal ore, forge the weapons, build the walls, and all the other tasks besides. Their life is hard, and they have to work from sunrise to sun-down to build and produce with sufficient output to keep the kingdom's armies and agents equipped. They have one day of rest, but that's often given over to medical aid, and new training for the constantly updated and refined methods they use. Dissent and freedom is limited, if they were to move out of their alloted role, the kingdom's productivity would collapse, and the tide of chaos would swallow it. Serfs know that the less they work, the more of them will, regretfully, have to be pressed into military service. Freedom is a privilege their nation cannot afford them.
Those above them are arranged in castes. The knights actually wield little power- after all their job is very dengerous, and they spend all their time training and fighting, so they have no time to run things. Knights are chosen for their martial skill and resourcefulness- after all they operate alone and in small bands, far from home or any support. The risk-takers and would be rebels of the kingdom, those who might otherwise dissent, are trained from an early age into a force of versatile, effective, and if need be, suicidally brave mounted warriors. It is in this way that the Knighthood has preserved life in dozens of small villages all over the land, and headed off disasterous incursions for hundereds of miles around the kingdom. Their calling is a grim one, and a softer, safer life is a privilege their duty cannot tolerate.
Leadership and policy is left to Wizards, Scribes, and others with the natural aptitude for planning and invention. These planners and leaders make a virtue of Disinterest, a dispasionate, logical view of events that allow them to remain unbiased, and make the best decision possible. Only in this way has the military and the knighthood been able to beat back forces many times it's own size, only in this way have the serfs been traned in the the most optimal and efficient methods. The leaders of the kingdom must operate from a position of pure logic and strategic acuity.
Compassion is a privilege that would only cloud their jugement.
What about the priests? The holy people of the Kingdom spend their lives in rapure, or torment, depending on how you see it. They can't afford to heal the sick, or offer their wisdom to the planners and policy makers, because put simply, they're too busy praying. Huge and intricate rituals are conducted by the clergy and their lay bretheren, who operate in a world apart from the rest of the kingdom. These rituals play many roles- they bolster the terrtory against extraplanar incursions, create grand auguries in order to determine and pre-empt the rise of great and apocalyptic threats, and harvest residuum from the Astral plane, which is used in more rituals and the creation of magical weapons and devices. Some Arcanists contribute to this process, but mostly it's organised around the faith, for only those of deep an abiding faith can endure the rigorous stress, pain, and sanity-shredding supernatural exposure that touches them in their every waking hour. The life of a terrestrial, flesh and blood creature is a privilege they can never know- their lives are spent in pain, blinding light, and endless prayers.
So there you have it. Who's want to live in a place like that? Sounds horrible. But they may well have a very good point, particularly if there are endless hordes of orcs in the wilderness, and various otherplanar beings straining to invade the natural world. Maybe they're right, and they need everyone in their lands to work as part of a machine, in order to prevent the destruction of cvilisation.
And sooner or later, they're bound to try and expand. They'd be unlikely to trouble smaller comunities- trying to force themself on small populations would be unethical and not result in effecitve outcomes- but if say, another city-state asks themf or help, they might decide to invade, and convert it to their grueling, machine-like approach to heroism. Meanwhile, the PCs are afforded much the same respect as knights, as long as they keep putting themselves on the line for the right cause.
But if the PCs dissent? Object to their regime, or plans for it to expand? Just imagine how those deliberatly callous planners, and their extremly formidable knights might respond.