Great Idea! Go ask the people of Darfur, Rwanda, or for that matter the Balkans how well diplomacy works against an armend thugocracy. Then swing by the UN and find out how well their efforts have worked, and stop by Canada to get a read on their national ‘peacekeeping’ roles around the world.
The cases you mentioned are all examples of ethnic cleansing, not attacks from outside. With the exception of Rwanda the other two are complicated by aspects of civil wars. Do you envision ethnic cleansing on seasteads? What purpose would it serve? If you want to live with a group of your own ethnicity, just go join one or start your own.