"It's very much a calculated thing, not an “instinct”. Social systems are driven by the signals the involved parties send each other. If you tell them “I won't retaliate”, they will act accordingly."
Uh, in dysfunctional settings this might be a valid strategy. Sure, I understand swift reprisal when the social code requires it for the individuals survival. But it's still a pathology - on the scale of the society. And luckily, not present in a modern civil society. If you live in such an environment then I am truly sorry for your current status.
And I claim we are partly at least talking two different things. Grudges spanning centuries between populations, and intra-population social dynamics are on two different levels.
Any way, if one needs to be vengeful to survive in a society I admit the root cause might not be the attitude of the agent-of-vengeance but deeper dysfunctions on a societal level.
The vengeance intent still produces absolutely no benefit to anyone.
" In the long run, the actions of a free nation, good or bad, can be entirely attributed to its people"
This would be a situation where the majority of population is actually driving the policy of the nation, instead of reacting to policies of the governing body. Usually it's the latter - the political elite and their network driving the political train. If there ever was a situation where the political leadership was simply enacting the "average will of the people" I would enjoy any references you can provide.
If the population is not driving the policies then it cannot be blaimed for the policies. Blaming the children of the perpetrators of any foul act is quite irrational (although practiced, yes, but still irrational and considered as such in civilized nations).
"Nonsense. Nationhood is as concrete as is your mother tongue and culture."
In general, nationhood as we understand it in the modern world is a fairly young concept politically. It's just one more football club to support. Mother tongue and culture are far more deeply rooted. For instance, Italy was a rambling collection of political entities after the roman times ended until Napoleon came and decided that governing the peninsula under one government was far more convenient. New club - one government.