You and @Justice and Rule
keep making this error and it is baffling.
The PCs are not the only murderers in a D&D game.
It is like you positing that others are suggesting PCs must be/want to be slavers.
That's really not what either of us are saying at all.
In a fantasy setting, there are reasons for the violence. Even if it's NPC against NPC, there's a reason. It might just be meta-reasons, but there are reasons. If you have a bad guy who just murders people for no
reason but to show how evil they are, then I think most people would think that's a poorly-done villain with uninteresting motives and/or that the GM is being unnecessarily edgy. There are a few exceptions, like if you have Joker-style villains, but the majority of bad guys have a reason
for their violence. But what's the justification for slavery? Just to show how evil someone is (as has been suggested elsewhere in this thread)? There's other ways to do that that don't involve slavery.
And may I remind you, this thread started because of Dark Sun, where slavery isn't considered so much a great evil to be overcome as it is a societal norm to be tolerated or even engaged with. And if slavery is a societal norm, then there actually is
a chance that the PCs might want to be slavers--or might end up as slaves. Didn't one of the first Dark Sun adventures have the PCs start out as slaves?
And again, what do you get
out of a game that includes slavery? If it's just realism, do you also have a Random STD table for when your players go a-wenching? If you have a PC with the Noble background, do you check to see what effects inbreeding had on them? "Sure, you can be a prince, but you're also going to take extra damage after each combat due to hemophilia." Since the party has encountered great horrors on their travels, do you insist that they have PTSD? All of these things are realistic
, and removing them from the game would, therefore, remove another crayon from the box and make the world less colorful, by the logic that's been going around this thread.
And if you say "well, magic will cure these things," then magic can also create constructs and animate objects to work the fields--and coin can hire some friendly giants to do the work of a dozen farmers (with plant magic to ensure bountiful crops to pay for it).
How do you think bad guys get into power? The very first AP Hoard of the Dragon Queen has you rescue a tortured half-elf Harper in the 2nd chapter. The first chapter has mercenaries and kobolds hired by the cultists pillage a town, presumably killing innocents in cold blood in the process.
I haven't read that one (we played in it briefly, but didn't finish it), but I imagine that there actually were
some reasons there.
There's also another difference between the violence and the slavery. Unless you have PCs or NPCs who are sadists (in which case, we're back to unnecessary edginess), the killing is fairly quick. And in a fantasy world, there's definitely an afterlife and a chance of resurrection. Slavery is a long, slow process that can involve a lifetime of abuse.
And just in case you don't get it, I literally don't care what you do with your home campaign. The (non D&D) setting I just co-wrote has some slavery and slavery-in-all-but-name in it, but I was careful to put legal limits on it in-game and to provide ways for the slaves to be freed because I know what's acceptable for my table. As it turned out, the player who probably would be considered the most "sensitive" by some people chose to play an ex-slave--and not only an ex-slave, but one from the culture where people were brainwashed from birth into thinking being enslaved was the norm.
And quite frankly, if someone else got a hand on my setting notes and said "I like the world and would want to run it, but this slavery has to go," my response would be "No problem; I have some ideas as to what else can be done, if you're interested."
But a company who is writing to a general audience doesn't
know what's acceptable for my table, and that's
what's important here. When it comes to a topic like slavery, which has not only harmed many people in the past but still
harms many people today (it's estimated there's about 50 million people who are currently enslaved), no game company is going to be able to write about slavery carefully enough. Whereas it's a safe bet that no gamers have ever been harmed by a kobold who was hired by dragon cultists. Sure, there are likely some gamers who had been attacked or even almost killed in the past, but being attacked by a kobold provides enough of a fantasy buffer that I'd bet most of those gamers would be OK--and that's not even taking into account that they'd also be playing people who can fight back.