As for your analogies, I don't think you can seriously compare stealing from your neighbor because he has a lifestyle you disagree with. The situation presented here is that there's a revolutionary medical resource that can help billions. You want to take that SPECIFIC scenario and turn it into a more general hypothetical one, but that's not what I'm arguing here.
Well, he sits on something you want very badly, for whatever reason, and doesn't want to give it to you, for whatever reason.
It might be a revolutionary medical resource, a revolutionary energy source or just an expensive vintage car rotting in his garage, whatever you find important.
If they actually presented the case to the Ba'ku, they might have even agreed with it. But they never did ask them. The Ba'ku were on defend mode from the very beginning because their privacy got invaded and then they found out the Federation wanted to secretly relocate them. You wouldn't trust someone doing that, wouldn't you? All they had was Picard who decided to take their side. Starfleet and the Son'a saw a group of "primitives" and thought they could simply do everything they want with them. And that's wrong, it has always been wrong, and it will always be wrong to do that. You can't just go and dictate how someone has to live because you are more powerful or have more people behind you and thus can dictate what's important and what's not.
Again, it's hard to argue ethics in the abstract. If it's a neighbor's car, you don't steal it. But what if you're starving, and you have to feed yourself and your family? Can you steal some food from your neighbor?(assume for the sake of this hypothetical you can't get public assistance or got a church pantry or something) See the problem in overly abstract hypotheticals?
And as for the Baku, I agree with you they should have been negotiated with. But again, that's a plot hole from the film, not a criticism of my argument.