In the conditions that gave rise to feudalism, modern democracy wold fail miserably and everyone would starve to death.
You can't isolate a society from the pressures around it or its technological limitations.
Without modern agrotech farming is extremely expensive and extremely risky. It requires a lot of land, a lot of labor, and is an absolute crapshoot depending on the weather. Independent farmers have no safety net. One long winter, one bout of crop disease, and their entire family starves to death. You can certainly understand why farmers do not like that solution. So instead they rent land from the rich guy who is legally obligated to provide them with a safety net. They can be sure that they won't starve to death unless everyone is starving to death.
It makes sense. It makes good sense. The land owner provides provides for your basic necessities as part of the rental agreement, and the agreement remains valid no matter who owns the land. And with your basic needed guaranteed to be taken care of (baring country-wide famine, which unfortunately does happen), you're better off than you could be an an independent farmer.
And then there are trade issues, defense, water rights, roads, and all sorts of other things that make pure anarco-syndicalist communes less feasible. All of that is usually taken care of by the guy you pay rent to.
There is nothing noble about attempting to tear down a system that works so that you can replace it with an unwanted and unpopular system that will most likely cause mass destitution and starvation. That doesn't make you a hero. At best it makes you a well-meaning moron.
Of course, with magitech that exists in D&D feudalism makes jack all sense. But most D&D societies aren't really feudalistic.
That's utterly wrong. Evil people have rights too. The laws of war are in effect even when fighting evil. That doesn't make them less evil.
That's extremely naive. It's a great principle, sure, but there will always be an urge to do evil unto evil, and the more your propaganda caricaturizes the opposition the easier it will be for your soldiers to slip up and do something silly. That's just human nature. In this case your soldiers would be the players. There is nothing wrong with the players having some guilt free orc genocide, it's good clean fun. But it might undermine the point that the game is trying to make.
Of course, the idea of an evil society also implies collective guilt with is pretty much anathema to any modern sense of justice.