Best to look at federated instances as more official, set-in-stone subreddits. They all (usually) have rules and most of the time the instance is not responsible for a single person doing actions like that. If a kick or ban is also swiftly given, that usually also voids the instance owners of any illegal content.

Any community is a valid community, if there’s 20 upvotes that’s still 20 people who saw, enjoyed, and gave it some time, and that matters on the modern internet where there’s a bit more gatekeeping than usual!