OK - In your scenario everyone has nukes... Isn’t nuclear genocide inevitable? The logic changes: Those willing to use them brutally WIN. Geographical concentrations of wealth, power, population are too tempting as targets. Reasoned, thinking, tolerant societies CEASE TO EXIST. Mutually Assured Destruction only works against organized nation-states. In this scenario, where the wealthy/powerful are under constant threat of extreme loss, the 'rational choice' is to do everything to avoid that massive loss - The only way to avoid the threat is to remove it completely... sudden and complete genocide of the threatening groups. As complete as possible. It won't work completely the first time. There will be some ‘leakers’ and the first to strike massively will also take big hits. But through persistent application they will significantly improve their chance of survival for another generation or so, for maybe another 50 years, until the next threat matures.