Every nation succumbs to its eventual death.  Usually moral degradation is the first sign of doom.  This leads to an unwillingness to support a military so the nation is susceptible to invasion or conquering.  Or, revolution may set in.  The detachment of a people from its traditions ushers in the revolutionary spirit; change for the sake of change, most often led by progressives of the day.

It would be great if everyone would disarm!  But the only way to make that happen is for the powerful to make it so, and if we disarm first, we lose that chance.  Our enemies won't abide by any such agreement.  Let's all treat others in the manner you suggest, but know that the largest number from among our human population will treat you much worse.  Being a Christian is either a death sentence, or cause to mistreat you in many parts of the world.