Evolution and the technology of nationalist movements
During 99% of the evolution of the human species, our ancestors were hunter gatherers fighting for survival in the African savannah. In that technological and environmental context, cooperation among members of the same group and distrust of members of outside groups was an optimal adaptive strategy. As a result, the human mind developed preferences that reinforced the own identity by opposition to other identities. These preferences have survived to our days, and can be seen in nationalist movements and in the emotions and sometimes dangerous tendencies of sports fans. The problem is that today the environmental and technological context have completely changed, and therefore a sharp distinction between "us" and "them" has become maladaptive to the majority of humans. We should cooperate more, at a larger scale. Of course, it is still useful to some people, for example those that benefit from the weapons of mass distraction that are nationalist movements, in Europe, Israel, Asia and many other places. Elites benefit from the mobilization of ethnic and religious feelings, as was predicted by John E. Roemer in an article where he explained why the poor do not expropriate the rich in democracies (because the rich are good at keeping the poor busy with identity clashes). Then the relatively poor (a good fraction of the majority) provide the labour factor in nationalist movements in the form of demonstrators and voters, and the elites, usually with the massive opportunist use of the resources and propaganda machines of rich regional governments (as in Quebec in the 1980s, or Scotland and Catalonia today), provide the capital. Of course, human capital also helps, especially where the labour factor is augmented by the power accumulated by well trained middle classes which, although being a minority (perhaps a cohesive and culturally homogeneous 30%), thanks to the structure of electoral laws, civil society and local institutions, may control the key nodes of society. Then, having a society mobilized on nationalism, but paralyzed on everything else, is perfectly possible. Political movements are the result of ideologies (beliefs), institutions and interests. But evolutionary forces and technology should not be underestimated.