"In the Grim Darkness of the Far Future, There is Only War."It's fairly easy to explain away a lot of fantasy game violence as heroes overcoming evil. In fantasy games, there is absolute evil. There are irredeemable monsters who were born evil, with an evil nature, who want to hurt the good folks. They need to be destroyed. They will never live in peace with us or see our point of view. There is no moral relativism, so the heroes, who are good, set out to defeat these foes who have done some sort of mid-level wrong (but nothing too heinous, because this is a game, after all). However, in the 40K universe, humans aren't any better than their foes. There is no inherent evil. So how do you justify the darkness?
It's not all grim darkness actually. It's considered a terrible heresy to turn on ones fellow humans (or super humans). Since all humans are devoted to fighting for the imperium, and the imperium's will is a substitute for the will of God, killing a man is a sacrilege. For what it's worth, just remember that all that war and killing is in defense of humanity, rather than the modern violence of man-on-man dogma and belief. One thing the 40K world has done is remove modern religion. Modern religion is divisive, so it was a clever move for the writers. Instead we have an emperor, and as humans tend to do, they've taken him as a god of their own. If you want to unite humanity and you had a magic wand, this would be your first step.
Human life is cheap, kinda. There are millions of worlds with billions of humans. Many worlds, especially "hive" worlds are heavily populated with 50-100 billion people. So even single worlds are populated more than modern Earth. I've been playing humans in 40K, also known as Imperial Guard, and the cheapness of their lives is something you have to come to terms with. Squads of troops are often refereed to as "speed bumps" for enemy troops. Only large "horde" armies of humans can win a battle. Men are referred to as being as cheap as ammunition, and spent just as quickly. So life is cheap, right? Not really. If you read the novels, which I've been doing, the heroes of the imperium are those who value human life, regret the loss of life, and generally have modern sensibilities towards war. Gaunt, Cain and other leaders of the Imperial Guard are heroes that value human life and work hard not to waste it.
The Empire is expanding. This is arguably the darkest part of the 40K universe. Part of expanding the empire is uniting humans under one umbrella. The first thing you learn, is that there are other humans, even other emperors, who have their own imperium and are quite happy to fight for it, thank you very much. These kinds of conflicts against other humans are seen as regrettable, but it's part of the mission of humanity, at least the humanity that we're reading about. Only a united humanity can survive against species that desire their destruction. As for planets inhabited by other species, they are subdued or exterminated, much like those species do to human inhabited worlds. This is the endless war part of the 40K milieu, seen as a mission to grow or die. If humanity isn't expanding, it means their enemies, intent on their destruction, are growing in power instead. Through a lens of violence of humans fighting humans, this is pretty dark. Through a species-vs-species prism, it's akin to something like men versus dinosaurs (although not historically accurate).
The Meta. I don't want to be an apologist, but most people don't read the fluff. I wish they would read more, as you've heard me railing about kids who don't own their own rulebooks and codices. At it's base level, the game is about modeling and painting, and for the most part people don't even play humans. They're too expensive and difficult to play well. People prefer to play genetically engineered super humans, scary robots, giant bugs, green monsters in red trucks, and similar sci-fi fun. Now that's the game that people recognize. As for the future being only war, remember the humble roots of the game. It was always about models (and still is), with a light science fiction background with plenty of monsters. The fluff came much later. In fact, a big criticism about the game is that the company sees itself as a model company, with all this fluff a sales driver. It's infuriating if you take it seriously, which they clearly don't.
My son is too young to play these games. Would I allow him to play them if he was old enough? First, I would be fairly cautious about the reading materials and would probably consider the fluff I've mentioned as adult fare, not suitable for a young mind. Second, there are some good values in this game. It gets kids off electronic games, which I see as the most corrupting influence in turning my kid into a zombie. It's a game that requires social interaction. Many fathers are playing with their sons and most kids get into it because other kids are playing (the key to any game). Third, it teaches kids to think. It has much more tactics than I originally thought, despite the giant handfuls of tiny dice that determine an army's fate.