Why are we fighting each other now? It's largely cultural and religious motivations, if we worked together as a planet we could get some really interesting things done.
“We” don’t have and don’t want to seriously fight each other. But it’s not “us” at the wheel. They have their own idea what we should do and until we get rid of them completely, your question will stay naive. This feature of our species was important for building civilization, but it will drag future generations down to the monkey bottom forever.