Maybe. But my very harsh judgment on the merits of nationalistic minorities mostly comes from reviewing cases such as the Balkans and Palestine.
I would deem that when natural cultural assimilation is possible, it is the best outcome. When unfortunately it is not, forced one or population transfers are a better outcome than Balkanization or ongoing strife from clashing nationalities. Population transfers in the last Century (e.g. Germany-Poland, Greece-Turkey) have managed to create lasting peace and development, even if some bad blood may linger, the clashes stand where those who cannot live together (eg. Cyprus, Bosnia, Kosovo) stubbornly cling to the same peice of land. And this is only in Europe.
Cultures that have something really worthy to provide to mankind, never really get exitinguished, they live on as part of the gestalt that is world culture. To all means and deeds, many cultures like Ancient Greek, Egyptian, and Norse cultures are dead, as the languages and countries that birthed them are extinct. To the matter of leaving a vibrant heritage, they are very living. I'm a strong believer in the worth of Darwinism as applied to cultures, if they are something worth, they most likely thrive and succeed as long as they remain vital, if they decay, their heritage lives on in other cultures. Having something positive to contribute does not mean that any single culture should be kept forvever under ice provided with an indepedent thorn-in-the-paw national state, state-enforced language and "cultural" output which nobody on the face of earth finds any spontaneous use or interest for, and an aggressive nationalism that does its best to inflict Balkanization grief on the rest of the poor world. Homer, Edda, and Ancient Nights have trusted the vagaries of history and succeded in all the ways that matter, even if Vikings, Greek city-states, and the caliphate of Bagdhad are dust. Why not modern Czech, Polish (referred to the conditions of the 1940s of course) Basque, Irish, Franco-Canadian, Serb, or Palestinian should be subject the same standard, and should be entitled to inflict grief and strife on the rest of the world, in order to artificially thrive under wraps ?
That's why I'm very, very fond of ATLs that build strong, world-encompassing empires, and totally loathing of ones that support Balkanization. Cheers and Hurrah for blobs on the map, I say.