[ZenGum]

Ok, here it is.

Everyone has to stop taking their make-believe game so seriously.
Everyone has to stop expecting other people to take their make-believe game as seriously as they do.
Everyone has to stop basing their world view on the idea that their imaginary friend promised this bit of real estate to them.
Everyone has to stop expecting other people to take the promises of their imaginary friend as seriously as they do.

That's good for a start, but the group identities of many of the groups involved also deeply involve hatred/resentment/desire to destroy one or more of the other groups. That has to go too.