what does that even mean
capefeather, what about nationalism, as a 'mental shortcut,' is in any way 'functional'
i think nationalism is ignorance (of what things have value, which is the same as ignorance of what things are a product of one's own agency) , or irrational egoism (thinking that shit is good because you are shit or you do shit), both of which seem bad to me, so fuck nationalism in theory. As has already been gestured at in the OP, nationalism frequently leads to awful states of affairs, so fuck nationalism in practice too. the best case for nationalism is nationalism as 'self-interest,' but i dont really think self-interest is a good basis for ethics, but thats like my opinion, so...
'it's only bad if taken to its extremes' is a joke, if ever a policy/law is put into place on the basis of an appeal to nationalism it will always be a bad policy, i promise. do you really feel such a strong need to apologize for nationalists just because a lot of people do it/or act out of a belief in nationalism? sorry, those people suck, you might even suck, the fact that you all suck together doesn't make it any better (interestingly, sucking together would seem to be the underlying condition for breeding nationalism), don't apologize by saying it only got bad when one of you took it too far.
Is Nationalism, by its very definition, a bad idea?
idk why don't you define it, i told you what i think it was but if we have different definitions then it's useless
i anticipate arguments like 'nationalism is necessary for state-like (government) structures to form,' guess the burden of proof would be on you in that case, so good luck finding any, and then even after that, you'd have to show that government isn't inherently bad (because if nationalism produces governments and governments are inherently bad, then you're no better off than before).
edit:
i really don't think nationalism should be reduced to the same terms as a group mentality. It IS a group mentality, but it is also many other things, and I don't see it as a fair analysis, given the complexity inherent in defining nationalism. I think you have to shred quite a few elements of nationalism for it to be the same as an animalistic species mentality. Especially when it gets to the policy level, as far as laws are concerned I don't think any policies that were good, were good because they were justified by nationalism, rather other forces such as economic forces might have driven these same policies and have been good because of that force's impact, not nationalism's. So these 'good' policies that we see nationalistic sentiments contributing to, does not mean nationalistic sentiments are good. And we can readily see the bad outcomes of nationalism sneaking into our legal systems across the globe (present france, greece, ww1/2 european great powers). so the good of nationalism isn't good because nationalism is good, it just contributes more sentiment to certain ways of framing issues, but the danger is that the good isn't separate from the bad, and it would be better to keep nationalism away from the ways policies are rationalized and argued on in general. it's an unnecessary risk and given the potential consequence it is unconscionable.