The scenario you paint here would only be true if a society's population truly were "enemies" and holding very different human beliefs, wants - which fortunately isn't the case - because the people of a nation evolve together generally; the problem arises when you mix two different people from different nations with different cultures, where this "50/50" destructive behaviour can exist - say when the native Americans were mostly wiped out, another scenario would be if somehow you dropped 10%+ of China's population into America all of a sudden or vice-versa. Historically this was a common war tactic - and still to this day we can see it in Canada, for example, with student protestors who are pro-China, indoctrinated into pro-China doctrine - the hypocrisy of having the freedom to protest in support of a nation state who disallows free speech and reigns supreme with censorship; we can't judge these people harshly, with compassion we understand they've been indoctrinated - their own safety and that of their friends and family may also rest in the balance - and it makes me feel like an important part of immigration should be education to de-brainwash them to make sure they understand these mechanisms of tyrants, suppression-repression of freedom, of control.

Otherwise you paint an unrealistic, bleak picture which isn't grounded in reality if there's optimism and humanity included.

"Otherwise you paint an unrealistic, bleak picture which isn't grounded in reality if there's optimism and humanity included."

True, still many western countries had examples of episodic police brutality causing tortures [1] and fatalities among protestors, and probably it was other people humanity and optimism, along with public outrage, to keep these events episodic. But the point is: what happens if after the first protestor dies the crowd doesn't disperse and the public is too distracted? I don't see either police or the military saying "oh sorry, we pushed it too much... feel free to continue but please don't smash windows". I also see as a revealing sign of corruption the almost ubiquitous police immunity: keeping them untouchable is what ensures their total alignment to the higher powers.

[1] plenty of examples in the 60s, also search for "genoa 2001 diaz": the Wikipedia article sums up pretty well what happened, and there are some rather graphic videos around showing it. That carnage, whose most explicit videos needed some time before surfacing, didn't make the news globally as it should have probably for happening less than 2 months before 9/11, an event which obviously hit the reset button on just about everything.

The biggest difference between now and "then" is the internet and our connectivity, audio and video + live streaming for real-time evidence gathering; yes, I'm aware bad actors are capable of signal jamming in an area or at scale, or taking down the internet - is why the democratic nations and people that are free must strengthen in case of a future confrontation with these bad actors, and likewise technology like mesh networks are expanding - although a nation could block mesh networks too with enough effort - and really then blocking communications is more a signal to the rest of the world that we're dealing with a tyrannical government.

Police brutality, lack of adequate accountability, is an evolving process that is trickling through society - through different states at different speeds: it's one of the values of giving relative sovereignty to each state so society can compare and contrast the different societal "experiments" based on their policies - allowing people to freedom to move between states and therefore the leadership they're under at the state level-context.