Xexizy here, I probably know more about 40k than I do about leftism, though that's not surprising ofc.
Lets have an overview quickly of some of the main races and their ideologies:
The Imperium of man kind are pretty much space nazis, with an emphasis on bureaucracy. They have many planets filled to the brim with people who work constantly to keep the Imperium maintained in various ways, though the majority of their manufacturing is done on Mars. Terra hasnt had any oceans for well over 20 thousand years, and is ruled by 'the high lords of terra' who do nothing all day. It's essentially an extreme oligarchy. They are probably under the most threat of any race, as they're stretched thin and not only have scary aliens after them, but also have to deal with the forces of chaos. This leads me onto how they're nazi's. At the slightest hint of heracy, like literally one person out of several billion even knowing of the existence of the forces of chaos, because of course the general imperial population is not told about these things, the entire planet will be literally destroyed with everyone on it. This clip sums up the Imperium. youtube.com/watch?v=-__lDKotIho
Forgive the shitty video I found through google, it's part of another series but I couldnt remember what episode out of like 50.
Next lets look at the forces of chaos. They're basically space nazis. They own entire worlds of slaves who they have either broken down over time or simply drugged out of consciousness, who toil away, building war machines and temples until they collapse and die. The warriors chill with daemons, and are extremely religious to their chaos gods. They will often study unholy scriptures while not fighting. Their leadership is basically survival of the fittest, with back stabbing happening frequently, and if a lord ever shows himself to be weak his men usually just kill him. Like the Imperium of man, they consider humanity to be the greatest race of all, and detest all forms of alien.
You also have the Eldar, who consider themselves to be the master race among all other races, even though they are dying off, much like nazis. Unlike nazis though, they all live on giant space ships which basically all work like communes. They have the best technology, and back when they ruled the universe they all literally had communism and never had to work. Because of this they all formed pleasure cults, started having wild orgies and their heightened senses and emotion spawned a new chaos god which killed about 95% of their population instantly. Basically communism leads to Slaneesh.
You also have the Tau, who are sometimes considered the commi hippies of the universe. This is just untrue, as they actually have a very strict cast society structure, and treat all other races that live with them like second class citizens, apart from the Ethereals who rule over them like philosopher kings. They are a small empire, but are growing rapidly. They are pretty much as brutal and ruthless as anyone else.
The necrons and tyranids are basically unconcious, or have some form of hive mind. They just want to kill things and have no real structure as they dont need it.
The orks also just want to kill things. Their leaders are literally decided on who's the biggest. No, not in that way, they're asexual fungi growths.
That's the main factions, I'm probably missing some of them though.
Essentially everyone's fucked.