This question seems to be posed in a moral context, specifically reference humanitarian disasters. You are coming at it from a legal aspect, which can be entirely disconnected from morality.
The question seems akin to a question like “If the villages in the area are being pillaged and the villagers need refuge, does the king have a right to keep his castle closed to villagers who didn’t work his fields just because he owns the castle.” or “Was it morally acceptable for Noah to not take any people other than his family onto the arc”.
I could be reading it entirely wrong, though.
2000 concurrent is absolutely unmanageable, but I feel most servers will deal with a 100:10:1 ratio between total users, active users, and concurrent users. That definitely isn’t a perfect rule of thumb but it’s usually what I observe on discord servers and subreddits alot of the time. Based on that, 2000 total users logged on a server would equate to about 200 active users who log in regularly, but only about 20 concurrent users online and posting at any one time.
EDIT: If we want to put the active users to dunbar’s number, though, we’re looking at 1500 total users per server. I don’t really think a single admin for any social space is really enough, as that means that most servers would go unmoderated the majority of any given day, while still putting alot of strain on that sole admin.
I think the solution is going to be more instances. Keeping the user count low per instance both allows human moderation to remain viable, and provides more niches for subcultures to grow. I think 2000 total users in an instance is safe manageable amount, so long as they are not all using the instance at once.
This poses new issues for the fediverse as a whole which I do not fully understand yet myself.
Anytime you enter a product into mass-production, you have to make compromises on the form - and the function in marginal ways - of your design. some shapes cannot be machined by CNC systems, parts can get stuck in molds if you design overhangs in them, etc. There are always a collection of limitations for any given manufacturing method.
This is a big reason why design flaws pop up on various products. worked great in the prototype, but tweaks ended up less effective to work on a factory line.
You can even get forced into certain manufacturing methods due to your design needing to meet certain requirements for its function (being affordable, having to withstand extreme stress or temperature, etc.)
I think they are asking “SHOULD states have a right to regulate immigration?” which is a much more complicated question to answer.