Nationalism was invented by Napoleon III, and he became Emperor because of it. It was a very profound idea that unified the French not by language but by the relics and ideals its Citizens held to be valuable to them; la Gloire de France, whether German or French by ethnic origin, on Principal it could be supported. Indeed, since then it has been exploited.
Like Napoleon, it was exploited by Ataturk, (and Hitler; to name two other significant players) not for the benefit of his population as a whole, but for the elite that surrounded him. It continues to be a source of plunder by those who take Humanity as something second place, to their own "ethnicity", as though blood is not blood, one and the same; as though Universal Principals are easily ignored. It is not Nationalism which is bad, it is the concepts that have been placed on it by the political class, for power.
Lest we Forget, the lesson of the First World War, enemies exist, but not each other. Hatred is good, against real enemies, like Hunger, Disease, and Ignorance.
Cypriots if given a chance can prove that there is some good in Nationalism, as Cypriots; rather than as how they have been divided, for "Greekness" and "Turkishness", whatever they may be, one in the same.