If it works anything like Mastodon, server instances may ban entire other instances from posting and interacting with their community. So you can't just create a terrorism instance and expect to be able to spam every other instance. For accounts on each instance, the admins will have to ban them just as any other account.
Basically a server owner can block an entire server from their own if they don't agree with the content or userbase they cater to.
It's a double-edge sword since a ban-happy server could isolate itself from the fediverse or create a worse echo-chamber; lucky for us, we can just create a new account in another server and just leave that one behind.
It's better not to attach yourself to your account and just think of it as disposable.
the reality is, there will end up a pocket group with this and other types of content, over time it will be effectively a shadow network. the blocking game will always be a thing.