Here's the fundamental problem: we need a hippie solution. Nothing but making the world more peaceful is going to reduce the risk of nuclear annihilation. Why's that? Because even if one nation conquered the planet, it would only wind up splitting from within and becoming multiple competing nations again. And it's a problem because warmongers tend to react violently against... well, everything. And violence is something that hippies aren't prepared to deal with.
I guess what's needed is a sort of warrior hippie.
We could call them Social Justice Warriors ;)
Seriously, though. There's no military solution to the threat of endless war. It really is true that only cooperation can solve this problem. It's not enough to hold hands and wish real hard, though. The lovers of peace have to become as creative and determined as the makers of war.