You can imagine all kinds of scenarios, but it comes down to "are users of server X forced to handle content from server Y". It can be both good and bad, but either way the Fediverse chose "no".
If the reason for "not forcing them to handle content from server Y" is that the admin of server X had a name calling spat with an individual user on server X, the fact that the fediverse makes instance admins into miniature dukes and dutchesses, complete with wars and Honor, is an unalloyed pain. ;-)
Again it doesn't really matter because it's just the way it works, but it's also a feature for server admins. Imagine being harassed by someone, or imagine that person harassing your users, blah blah blah. Is there some hypothetical where this feature is abused in a super petty way? Sure. Welcome to all features in all software.
Let's take a gun as an example. You could use it to shoot a bad guy, but there are a lot of times where the person who got shot was a good guy, and a lot of other times it's by accident. The same goes for moderation - you can justify handing out the power to cut off connections between entire communities to random people by thinking of the ways it could be used for good but it doesn't get you out of dealing with the ways it can be used to harm.
You could say the exact same thing if federation could be forced. You can make whatever facile analogy you want; my point has always been there's bad scenarios no matter what.