Nationalism has nothing to do with hate, as said. Even if viewed as perceiving your country to be superior to others, it has nothing to do with hate. I am superior to ants and other beasts, my students, and all manner of other things that dwell on this planet. This doesn't mean I hate them because they are inferior, nor that I really give them any regard at all. Such is the same with my nation and my people. I believe and know they are better than the rest. Doesn't mean that I hate the rest, or want to gas them. And even then, the notion of regarding the nation as superior is not the same as nationalism, just one variant of it.
Equating nationalism to an extreme tangent of itself is quite erroneous; placing the likes of Garibaldi on the same pedestal with the Fuhrer is a rather perverse comparison.
You can take nationalism, put it in a black cauldron, add a host of other factors and catalysts, let in boil, and create a witches brew of Nazism or the like. An extreme byproduct is not the same as the original material.
Indeed, it takes less of the opposite ingredient, supranationalism, to create the end product of socialism and communism, which have a body count that puts Uncle Adi in the Little League, and rank just as well in the Evil 500 Index.
If anything, nationalism has saved, shaped and made Europe, particularly in the 20th century. If we look at what proceeded it, we see large monolithic supranational empires. If we remove nationalism from the course of history, and let these continental empires continue their regular wars and conflicts in combination with modern technology, then we soon get a far bigger body count. Several Great Wars, without various nationalist factors, of increasing destruction.
Nationalism did not die in 1990; if anything, that was the beginning of its rebirth, and current thriving.
The predecessor to the notion of Europe, Christendom, was not marked by any cessation of conflict or happy utopia, nor were such entities as the Holy Roman Empire.
Love and hate are simply the same emotion of extreme intensity, variant on which side of the mirror ye are on.
Too determined to hear what others have to say. Nationalism is pride of one's country. To be proud of something does not mean that you hate everything else.
Patriotism and nationalism are two forms of the same thing, a pride and love of one identity group (defined in terms of ethnicity, language, culture, history, etc) and the wish to advance the standing of this identity group. Its goodness and badness depend of the circumstances and the viewpoint. 
