's analysis is excellent. You can't truly understand an entire civilization with a blanket stereotype. Human nature includes everything from Gandhi to Hitler, from Kirk to Khan. Vulcan nature includes everything from Surak to V'Las. We've seen some friendly Tholians in Vanguard
and elsewhere. We've seen Romulan dissidents who sincerely want to reunite with Vulcan and don't share their government's attitudes. And so on. Any blanket generalization you can make describes, at best, the prevailing attitudes of those who currently
hold political or cultural dominance within the society. But every society has its dissenters, its internal disputes and disagreements. Any ruling ideology is going to have competition within the society and will sometimes give way to it. Heck, look how quickly the ideology of the United States government has changed since last year.
There's no such thing as a warlike species or a paranoid species or a diplomatic species. Those are racial stereotypes and are wrong on the face of it. There are only civilizations or nation-states whose current leaders or prevailing cultural mores are warlike or paranoid or diplomatic or whatever. But cultures tend to go in cycles and regimes inevitably change.