Imagine!

In his song "Imagine," John Lennon envisioned a halcyon world devoid of borders and gods ("nothing to kill or die for"). But theism and nationalism (and racism and all the other isms) are more often excuses than explanations for human bloodlust. We kill because we enjoy killing. A propensity to kill ("fight or flight") is deeply embedded in our genes, accompanied by a hormonally-mediated "high." On at least an elemental level, killing feels good! Absent a greater reliance on Reason to subdue our passions, we will likely continue to find or invent "reasons" to kill each other.

"Fight or flight" prepares us not for a gentlemanly bout of fisticuffs but to rip each other's throats out!