There's a legal doctrine called necessity where breaking the law is justified if there is no lawful way to achieve the same end and the end avoids greater harm than violating the law causes. For instance, driving drunk because you are the only person who can take an injured person to the hospital. By comparison, intentionally killing someone who poses you no threat is never considered justified.
Ah, but that last sentence, so simple sounding, is where it gets interesting. People who stand to gain from your death contrive reasons that you are a threat. They even convince themselves that they are harmed by the existence of another (consider the word "systemic") or their hold on property, no matter how rightly owned, or power, no matter how justly adjudicated. They believe the world would be better if they had that bit of property, or that hold on power, and your opposition to their growth at your expense is "harming them".
In a way, this is entirely right. Our cities don't have to be hellholes, but they are because they are filled with fundamentally bad/incompatible people. We even once had nice cities, and there are still examples of nice cities showing clearly what it takes, and what it takes less of, to have them. Even if you don't care for nice cities, what is true for the cities is also true of wider culture, and that which is imposed on those outside cities. There is no argument about this, yet certain other forces see the opposite. These people aren't fundamentally bad, they think, they are ideal consumers, and are less likely to persecute us for our very righteous stewardship of money and media. What's a dirty street corner, a rape or two, and the genocide of those who instinctively hate subversives like us (for no good reason, I might add) compared to that grand cause? Or so they think in marginally different words.
And to reverse it again, we would have a better civilization without this subversive, parasitic element which benefits from making things worse for us. Rather, this inherent conflict between better for me vs better for you is the real nature of war. Both sides are right that the world would be a better place for them without the other. Neither is wrong for recognizing this, or, despite what a pacifist might say, deciding to wage war.
However, this "both sides r just self interested" universalism is for faggots and losers, and it is one side in particular that makes the world an uglier, more deceptive place. They are evil in the truest sense of the word, and God willing shall be expunged.
