Well, I'm surprised, not too many people understand how the dark fantasy works and how it means...even for some who claim to read the rulebook...I thought you Westerners would see through this immediately, unlike an Asian as me...
Warhammer 40K is a dark fantasy, and the Imperium of Man is a future version of "medieval" europe, see the point? It isn't so unified, some people don't like Chaos, but neither do they like IoM, they are in between, and almost inevitably become Chaos-twisted, because of the pressure.
The commissar in IoM explain clear enough of what IoM refers to, or at least part of. You can easily see its connection to Soviet, that's how IoM works, and "how it taught its people", if you are clever enough to see. IoM taught its people to "fight for Imperium glory, and fight for human's survival", doesn't this seem like how society teach us, especially in some autocratic countries?
If you don't believe what I said and think of this as coincidence, then let's look to the rulebooks, anyone who claims to ever look to rulebook read of Armageddon War I, the infamous campaign against Chaos intruders? WHAT HAPPENED, in the end, to those Imperium soldiers, and those who sighted Chaos existence? It was pretty clear how "against-war" 40K stories are, as long as you're clever enough to see it. That's how IoM treat back those who fight for it.
And what would it mean? Let's go back and see the totem of IoM, the Emperor, he seems like a savior, a god, the one who, commoners must serve. But WHAT ABOUT NOW? He's only a body lying on Golden Throne, you thought he was hope, but this hope isn't within reach. IT WASN'T ,and NEVER WILL IT. Instead, look at those who rule IoM for the holy Emperor himself? The High Lords of Terra? The Mechanism? Space Marines? They're only dictators, arm dealers, and warlords, if you're clever enough to see through this. The IoM is DOOMED, DESTINED to. Look at those seemingly-evil race like Chaos or Tyranids, they're TRUE Evils, but if you think on the other hand, IoM is good, then you are wrong, damn wrong. They are craps, an autocratic empire WHO DOESN'T CARE ITS PEOPLE, and TEACH ITS PEOPLE TO DIE FOR A DEAD MAN, who is kind of like Jesus, the one we don't quite believe in modern days, and the IoM as Papal states. You SEE THE POINT? This is AN IRONY, IF YOU'RE CLEVER ENOUGH TO SEE.
There is almost only DESPAIR in WH40K, BECAUSE EITHER WAY, EITHER RACE YOU CHOOSE, IoM is DOOMED, HUMANITY IS DOOMED, Eldar is DOOMED, THE GOOD FORCES ARE DOOMED, the only one, who are more positive, is Tau, and their TERRITORY IS SMALL, and it's UNLIKELY they can develop FAST ENOUGH TO STOP THE EVIL, not to mention that they disdain Warp tech, which is pretty important in Galaxy.
So there is ONLY DESPAIR, ONLY WAR, ONLY DOOM, that is coming, AND YOU WON'T GET REDEEMED HOWEVER HARD YOU TRY. It's the European in 80s which create this, you can see it from the atmosphere of the decade; it's the dark history of Western civilization, or even to whole human history, which should be apparent if, any of those who complained, have learned a good history.
So that's how warhammer players feel, you PLAY IN A WAR GAME, and you learn from it, LEARN THAT WAR IS EVEN HARSHER THAN ANYONE THOUGHT, learn that WHAT WE THOUGHT WOULD BE TRUE, MAY BE ONLY LIES THAT GOVERNMENT TOLD US, just as what Nazist told its people. Which games you guys play don't kill anyone nor any monster? Very few, but that's not something you would learn from, because you never look into how harsh war is, because you never think of how the terrible thoghts were implemented into your mind, because you kill and think of it as normal(in game), BECAUSE YOU ONLY AVOIDED FACING IT.
That's how we( or at least I, I'm really surprised that few in this forum thought of these) play warhammer 40000, we PLAY IN WAR, and we DISDAIN WAR.