So I've been considering running D&D in an exotic-ish setting (ref), but I think there's a broad issue about this.
In D&D and other games with an absolute good and evil, it's usually true that good and evil are defined by modern standards. So, for example, D&D has always defined slavery as evil - even though slavery of various sorts was considered normal and even good in medieval times. I think this is usually considered a feature rather than a bug. In some games, you play grim-dark bastards who leave a trail of horror and destruction -- but some fantasy games you want to be genuine heroes who fight for truth and justice. There is simple good and evil and the heroes are good.
The latter is more what I want my upcoming D&D game to be. Real history was often grim and horrible, but if I'm playing a good-vs-evil fantasy, that's not what I'm looking for. I'm going for more escapist high fantasy.
The problem is that modern morality can be a disconnect with a setting even remotely based on history.
So I guess this is about - when have you had a problem with difference between what is good by modern morality and good in a fantasy RPG? What were ways that you dealt with it? I'll think if I can come up with some more examples.
This is a potentially great thread in the making. I plan on participating.
I do think you mischaracterize one point...
The problem is that modern morality can be a disconnect with a setting even remotely based on history.
"Modern" players do not fundamentally understand "morality". It's a word without meaning to those that freak out about "slavery" as a topic. They associate anything that makes them feel "SQUEE" with "BAD" and therefore "EVIL" and anything they like as "GOOD" without a grain of moral reference.
This phenomenon is underscored by an insane level of ignorance of history. A childlike naivete about civilizational development and sustenance.
Slavery is a historical norm. Every "great" culture in history practiced it or was part of it. It remains true to this day - we just disguise it under other systems with cleverly re-worded blinds and convenient political covers that don't seem to be an issue to those that pretend they hold "slavery" as some kind of ultimate evil.
To the point of your question:
I have never had a problem at my table with people confusing reality and their personal morality with the things that happen in my game. I have had very devout religious players, pagans, atheists, Christians, agnostics, each with their specific beliefs of varying degrees of rigidity, and never had an "issue". I assume by issue you mean people being so repulsed by what has happened in the game it affronts their own actual morality? It's never happened because no one at my table is so stupid to believe what people's PC's do, and what elements I have in my games is based on how I or the other people feel and believe the world outside of the game should be.
Maybe I'm lucky? I doubt it.
But at my table *everything* and *anything* is possible depending on the circumstances. I let things get as dark as they demand. And I've had some really dark moments (My Sabbat games are pretty grueling), but I'd also say I have some really ecstatic moments too where I'm always trying to elevate my players by making them realize the morality of their choices often have results that transcend their actual intentions - this has an intensely powerful effect that gets players to immerse themselves in the game.
The whole "Hey yeah, *I* did that?!?!?" effect. Of course it cuts both ways.
I think this is the big attractor I have with players that come to my table and they stick around for *decades*. I serve up gaming experiences that are equally morally challenging as they are rewarding from a gaming perspective. And I would like to emphasize - I generally don't aim for *dark* campaigns, and I Session Zero that upfront when I'm kicking off something, I want everyone to make sure they understand the basic tone of the game, but I'm also open to letting that shift based on the gameplay.