How can we fight each other knowing all we know?

There are many reasons for us all to come together as one people of one world.
For humanity, there are human reasons which will all know in our hearts as true.
As we see the truths of why we should live as one, we see our greater responsibility as caretakers of the earth and all of life. In this truth we may sacrifice all human war, and all of human suffering, save the suffering of love which we can never sacrifice, and live for life.

No matter what we do, time will not yield and the world we know now will not last forever.  The continents continue to shift and stars explode eventually.
So it is in our best interest to do everything we can do to survive and overcome these obstacles threatening the extinction of life.

From a mass of particles, gravity sparked stars.  Stars become the engineers of elements in there fusion and planet forming gravity, and sow their elemental seeds across the universe in super nova explosions.  It seems, eons of atomic evolution have finally created an organism to understand the eons it took to generate the spark of life, of understanding.

How can we fight each other knowing all we know?
Why can we not use our technologies to give life a better chance to survive, rather than kill people?