Just a user here, but I'd say a small subset of users in other instances are already asking to defederate from this instance for some of the basic communities that show up, like gonewild. I just don't see allowing a fetish "at this time" being helpful to the situation.
The mod tools are not there yet, even if you added the ability to opt-in on just this instance. If someone subscribes to the community from a different instance it will show up for ALL USERS on the all feed for that instance. And well, thats just shitty (pun intended) for those who don't like the kink but want to see nsfw communities. Now you've put the problem on the users who must choose to block the community.
So, while I'm a big supporter of kinks, I am not in support of allowing it on lemmy today. voted accordingly.