Slavery was considered OK in quite a few time periods and places...ancient Greece and Rome come to mind as the most familiar, but let's not forget Africa (a lot of American slaves were bought from African warlords), Arabic slave traders, Ottoman janissaries, and so on.
A few games, largely out of print from what I can see, with explicitly anticommunist themes have been mentioned. I think there were explicit attempts to make Christian RPGs but none of them have become popular. Dragonlance actually had some Christian themes--the Hickmans are Mormons. A lot of Mormons have mastered the art of producing Christian-influenced stuff that isn't explicitly preachy, from what I can see.
It's not really anticommunist, but the d20 setting Midnight had a large oppressive evil empire that tries to wipe out clerics. The idea is basically 'Lord of the Rings if Sauron won'. It's pretty dark though, as you might expect.
I believe Steve Jackson is a libertarian and GURPS books often seemed to have a little bit of that in them, though it's subtle.
Espionage-themed modern games could easily focus on the Cold War.
Cold War sci-fi often analogized the Communists to a hive mind (they all think the same and are willing to die for the hive), so any battle against an insect enemy could have anticommunist themes. Formians in particular were lawful neutral and were depicted in 3rd edition as invading places and trying to compel the locals into labor.
Major anticommunist themes included the uniformity and antireligiosity of Communist regimes, so typical monsters might be golems, hobgoblins (militaristic and organized), fire giants (same), or devils (which are lawful evil and probably masters at propaganda).
The drow are pretty organized and sneaky, but with all the infighting are closer to ruthless capitalists--Moscow held a pretty tight rein on Eastern Europe most of the time. (The matriarchal society could be great for SJW jokes, though.)
(Ironically, the left-wing and quite SJW Sigmata actually has a few right-wing player options--you can be rural libertarians or corporate capitalist types trying to overthrow the fascist government.)