Racism being normal ...
Trying to think of a game where its not wrapped into the normal 'slaughter everyone on that side'. with no particular actions expressing racism overtly
In some places in the world its perfectly acceptable to kill members of 'that tribe' or ethnic group (is that racism when you are killing them because they are 'the enemy' ) also the religionism (sectarianism) similarly
Lord of The RIngs -- the heroes there could probably all say 'the only good Orc is a dead Orc"
Now the whole outside goals of the confict may originate in racism ("we are the superior race and we deserve to rule them and any who dont like it and resist we should kill...") But players arent given a chance to modify the whole setting of the game to change that.
I recall in Ultima Online they had 'red' marked characters (killers of NPCs or Players) who would be attacked by guards in town, but it was so easy to have a seperate 'gopher' char to do everything in town you needed so it wasnt such a great penalty. Also getting away was very easy allowing chronic ambushes of newbies by griefers and them running if anyone 'hunting a red' turned up . They (the company) eventually spilt the entire world into 2 near duplicate maps with one being no PVP at all allowed (before that heavy handed change, they tried some very byzantine rules dealing with when you turned 'red' and how long it lasted and such -- which never stopped the mentally ill newbie killers from getting their jollies.).
As for morals being implemented variably (different from our normal society or also different from place to place within the game) then the player has to figure out how far they can go (or what is acceptable0. Some places where it might be as limited as simply insulting someone leads to them wanting to kill you and places where there is also noone to stop them from carrying it out. That still calls for alot more complex/detailed social interactions than we normally get (without it being a staged/choregraphed scene you are led thru by the nose).
Imagine a social etiquette tutorial (or series of them) players would have to be given to understand some exotic society, particularly if repercussions in the game are costly to the player for breaches of 'expected' behavior.