As you say, it’s a very blunt tool and likely only able to create more civil interactions by creating a fairly strong echo chamber.
My perspective on “defederation” conversations, hinted at in my comment above, is that it’s a new “tool”, a new phenomenon etc. Nothing like it existed on reddit for example. And so it’s natural that there will be “unwise”, premature and overzealous calls to use it as though it’s the solution to many of our social media problems, when in reality it’s a relatively subtle tool best used in concert with active and relatively sophisticated community building and organising.
Which all makes sense to me. But what’s a little sad I think is that we have here a pretty good compromise between “absolute free speech is bad” and “censorship is bad” for social media, and instead of embracing it as an ideology we’ve gotten some loud voices eager to use it as a territorial weapon for drawing boundaries around spaces for everyone else without, AFAICT, much the same in the way of actually building spaces that suit people’s needs (though that happens too of course).
If one wants or needs a space that is shut off completely from what one would call “extreme” politics, that’s totally fine. Doesn’t mean all of lemmy world and half or more of the communities on lemmy should be cut off in a big “us and them” statement. Instead … you probably need an instance that caters to that world view. You may need to try to start organising it yourself if it doesn’t exist. Except, that’s harder than posting a “lets defederate” post.