So diplomacy is out, it just won't work and you can't force people to like you when your efforts to do so are perceived as an insult of the deepest nature.
That leaves the complete and utter destruction of their mindset through force and breaking down their false sense of superiority so that we may build them up again and teach them to create a world where they can be proud of themselves, while simultaneously respecting the right of other groups to be proud of themselves as well. That's what it comes down - tolerance. Until they stop thinking of themselves as being better, they cannot possibly live in peace with the world. We must break this pattern of thinking at the molecular level.
The solution is pretty difficult. Note what T.C.Schelling and J.M.Epstein said respectively.