So this is controversial eh.
Here's a predicament I've been toying with for a few months now:
Ethnicity is a social construction and so it's contingent and depends entirely on the material conditions from which it arises. Thus ethnicity, and by extension, nationalism, are only elevated in social systems where it makes sense to identify with a 'nation'. So you don't really see much nationalism in the middle ages because feudalism masks it (loyalty to your lord, not your king etc)... and it only really comes to the fore after the French Revolution when the modern nation state emerges. So, rather than identify with fellow workers from, say, the same union, reactionaries in power emphasize identification along national lines. This masks the class divisions within a society and so undermines the workers' struggle.
So the problem with the Revolution is partly nationalist sentiment cutting across classes and making workers feel as if they DO identify with a nation instead of with their fellow workers (who, incidentally, share the same relation to the mode of production as their colleagues and thus have the same fundamental interests in mind).
So... in order to have a successful Revolution and subsequently a successful socialist state, it becomes necessary to undermine and eventually destroy nationalism. But this means that sooner or later individual cultures are going to die out. Does this mean that I can't be both a Marxist and an Armenian?
I have an answer, but I'd rather hear what everyone else has to say first. You know, to promote discussion and whatnot. Like you're supposed to do in forums.