If you don't look into the functional, adaptive qualities of conflict in humans, you are going to see it as a problem to be solved, without recognising the costs of eliminating it. Consider the arguments in my answer here: If we had the ability to make humanity less war-like, should we?
The research quoted about the beginning, described how a majority of murders of strangers, happen over very minor interactions, that can be understood as status conflicts. And we can see those as driven by responding to inequality, and increased status competition. The research says status competition doesn't go away in more egalitarian societies, it is just able to find healthier outlets, like say sports & hobbies, instead of fighting for gang turf to avoid starvation.
I would relate being willing to die for others, and for ideas like pride (eg the kleos aphthiton of the Ancient Greeks, 'everlasting renown'), as key to humans entering a phase of deeper cooperation and group meme-spheres that we call culture. Discussed here: Which philosophers believe freedom (liberty) is more important than one's own life and how did they argue this? It's a powerful & ancient 'circuit', and it can be manipulated from within by vanity or without by nationalism. But it can also be the engine of human progress, when people die for what they believe in - like Ukrainians are now, to not be ruled like Russians and face another Holodomor.
The Mongol invasions were kicked of by two really extreme winters killing off so much livestock they saw no other alternatives but to go raiding. Chinese revolutions & civil wars have almost always been linked to flood, drought, and/or famine. Most recently, the Syrian civil war was linked to drought, and government indifference to starving farmers with nothing to lose.
A single world government would be vulnerable to collapse, like the dynasties of the Chinese state. And the Needham Question shows how the cornerstones of the modern age (gunpowder, magnetic compass, cabal locks, paper, & even ocean going Treasure Ships) all occurred earlier in China, but the modern age did not. A similar case can be made about the lack of social progress in Ancient Rome, ie slavery, & inability to undergo an industrial revolution despite having mine-pumps & the core concept of steam engines.
Humans do well competing in groups. We need regulation to make that competition healthy, and curb violence and destruction wherever possible. We need this to act as a laboratory for how to move forward, and if there is a region that has it, in the long run it will outdevelop a region that doesn't. In China it was the Han living in the marshes, that developed stable Confucian rule after unstable centralised Qin rule, which allowed no regional autonomy. Europe was exceptionally hard to unify & keep that way because of few large river deltas & impenetrable forests & marshes, helping lead to reform of biblical prohibition of usary because it was so significant to winning wars - and that ended feudalism. In the modern era, we simulate tribal conflict and the rise & fall of empires & dynasties, in the business & political worlds.
I would suggest having different regions actively trying out different cultural dynamics, in a way that sees successful ideas spread, is crucial to avoiding technological and social stagnation.