Except in the current disorganized world we always just end up with one or two superpowers bullying the little governments and crushing all kinds of diversity anyway.

Also,

You can move to a country with less oppressive laws

That might work for the crafty and well-resourced individual who has a go bag and good OpSec and can actually hop borders and keep their heads down, but that sort of thing is nearly impossible for, like, a single parent working for a crap hourly wage, or an unhoused person dealing with an extended mental health crisis, or other more vulnerable people. Justice shouldn't depend on geography.

Only matters because of corruption and bad actors. Like I said, that kind of world would require a huge change to human nature itself to work. Whether it's 1 global government, or full anarchy.

Besides earth federation would subvert any diversity we as humanity have.

You can have political / economic union but cultural diversity. In fact you can even have political and legal diversity among the subdivisions. There already are a bunch of countries that work like this, such as Malaysia, Nigeria and Belgium.