OK. Just think we've gotta ask the questions.
Another is, what do we do about some self-proclaimed overlord who says:
"No, I will not hold a plebiscite, my people are loyal to me just fine and I'm doing just fine here," when we have good reason to think all is not well and that they're terrorizing people? Sovereignty without democracy is... ideologically tricky for us.
I mean, there's a very obvious set of stages to escalate with. Demand that they tolerate outside observers, reporting on if their claims are the case, and free movement of anyone that isn't comfortable living under those circumstances.
If they refuse, consider that a piece of evidence towards a formal casus belli. "They do not allow for the people to select leaders of their choosing, they do not allow outside verification of the wellbeing of the people, they do not allow free movement of the people..."
If outside reporters report coercion, start with diplomatic and public pressure and condemnation of their actions and demand that they change that status.
Overlords may not be targets by
default, ideologically, but that's with the understanding that they've been under uniquely difficult circumstances and prolonged social breakdown and may have not had the opportunity to reassess the merits of representing the will of their people. They will be given
several chances and incentives to do so.
In other words, they
had excuses to not get with the program. That excuse has an expiration date.
Basically what clockworkchaos said:
I am totally fine being the aggressor in wars for the sake of enforcing terms like "you will let our shipping pass through" or "you won't harass travelers" or whatever. I am not fine with annexation.
If our expansion hits a hard limit because the expressed will of the people in all our neighboring states is "we would like to keep doing what we're doing instead of joining you," I consider that feature and not bug. I can live with not stretching from sea to shining sea if the people on either side are happy in the polities they're in.
Forced annexation of acceptable variations on self-governance isn't on the table, no- but frankly, we should aim for a)representative government, b)finding states that are okay with or expanding into some sort of union from sea to sea. (I mean, let's be honest, if we get NY and Cali on board, that's that goal technically achieved right there without any further fuss)
As for here and now...
Velvet then glove.
[X] Remove Hostile Neighborhood. You have been the focus of low-grade hostility and resentment for too long. And...well, all right, you've not actually been very proactive about doing anything about that. But you are
tired of it, and you will never get a chance to be surer than now that you'll have the ultimate opportunity to finally change people's perceptions of you. You can't make a second first impression, but you can kill that bastard first impression while you have the chance.