It's just like Animal Crossing...what's the problem? But then we remember that this is an online game, so I'll have to turn my thinking around anyway...
It's no secret that the bulk of the issues with online games can be attributed to players: moderation is subjective and good moderation is expensive; there will always be loopholes or uncooperative users, even if the game itself is completely morally sound, there will be at least 1 player to make it otherwise. It goes without saying that there needs to be a comprehensive and clear set of rules and a clear reporting system in-game.
The game isn't aimed at children, but being online, there will have to be some effort (or at the very least, a disclaimer) to prevent children from being able to create an account.
For some time while the game is in active development up until a stable release, I aim to collect usage statistics such as computational power, screen resolutions and time logged in through an opt-out scheme. I also plan to have an opt-in system that randomly takes screenshots of the game and uploads them to Imgur for promotional purposes.
There isn't going to be any remotely sexist, homophobic or hateful content (or anything that could even remotely be misconstrued as such) because it simply isn't a part of the content.
Note that I didn't say "racism". While there is no actual racist intent, there are plans for real-time events throughout the year for various culteral holidays that distribute cultural-related clothing and furniture options, being seen as culteral appropriation is a concern.
The best I can do here is to ensure that I do my research on each event to ensure that I do them justice and bring awareness to what could be a uniting time.