Greetings!
Eh, I suppose I include various strands of social commentary worked through adventures, but it isn't something that I construct to beat my players over the head with. I generally make an effort at weaving through the campaign themes that are positive, cast against a backdrop of unspeakable evil and wickedness.
I have an evil empire that institutes--
(1) A set of universal rights for citizens, including equal rights for women;
(2) A massive, large-scale redistribution of wealth, (because they believe that wealthy merchants shouldn't be so wealthy;
(3) Free social welfare for the masses of poor Beastmen and Humans;
(4) Throughout the cities, non-military are not permitted to have weaponry without purchasing expensive licenses; Wizards and Sorcerers must have a license; (which is quite expensive)
(5) The Evil Theocratic Empire imposes high taxes on all citizens.
(6) The Evil Theocratic Empire accepts all races, but other religions are savagely persecuted. To enjoy the benefits of this powerful, evil empire, you must agree to convert to worship of the Dark Gods.
(7) Those who refuse to worship the Dark Gods are either killed and eaten, or they are enslaved by the millions!
(8) Decadance, Perversion, and rampant Hedonism are celebrated and unfettered by the imposition of laws.
(9) Certain groups within the realm have their children routinely taken away from them at a young age, in order to be raised on special government farms.
(10) Undead are allowed to roam freely, and Necromancy is a highly honoured and respected discipline.
(11) Cruelty and ruthless might are held to be absolute values. Torture is not only acceptable, it is encouraged as a matter of course.
(12) The evil emperor has absolute authority to kill, rape, slaughter, and torture anyone throughout the empire. His will is obeyed as if spoken from on high.
So, there are some of the evil themes that an evil empire in my campaign embrace. The players sometimes have to contend with these kinds of things, but it varies.

The players are kept very busy.
Hey Teflon Billy! My friend, you remember what my paladins can be like, huh?
Your paladins sound beautiful Teflon!
Semper Fidelis,
SHARK