The laws of human behavior are certainly less fundamental to the iniverse than the laws of physics, but, since we are humans, they are equally as binding on us.
Human behavior, and human society, have changed tremendously through the ages. It's the fastest sort of "evolution", to stretch that term a bit.
Plus there's nothing natural about widespread global war. It's not like you getting angry at your neighbor over some domestic dispute. Global wars are artificially engineered by guys who want to profit from them. It's not "human nature". Those willing to go to war exploit human nature, sure, but this is done intentionally; and just as intentionally, it could be downplayed or mitigated.
And if it's about egoism and greed, we've learned to reign those in in multiple situations. If we can attempt to go to Mars or whatever, I'm sure we can first try to sort things out on Earth.
Get out of your mindset. It's bad for you.
In Cosmos 2, Neil de Grasse Tyson has a reflection about that saying, "what are you going to do? It's human nature!". I encourage you to find the clip on YouTube and watch it.
Edit: well, I wanted to find the transcript or clip, but I cannot now. The Cosmos sequels are infuriatingly hard to find, and in my country there are no legal ways of watching them anymore (fuck you, Netflix and Disney! I pay you yet you remove stuff I like).
Here's Sagan's last paragraphs from his Pale Blue Dot speech instead:
"The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.
It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known."
