on a smaller scale it’s harder to form a group that would argue for necessary support for these people

Idk, I kinda gotta disagree with that. Sure, mob violence against "undesirables" is always gonna be a problem, but communities know each other and are less likely to see different constituent groups as "outsiders"

But in this specific example, where we are talking about "how do we decide who gets to use violence to keep the peace," I think community-based democratic approaches are the best option.

I also gotta disagree with

that community will still have its marginalized groups that don’t get representation

because by definition, if there is a marginalized group, they are not part of that community, and instead would form their own peacekeepers, like Guardian Angels.

Obviously there is a benefit to federalization, I'm not arguing for nor do I support statelessness, but I think if democracy is emphasized from the ground up, those issues naturally tend to erode. Like I think the core problem which necessitates the federal government stepping in to ensure rights comes from a lack of democracy.