Actually, given the possibility of global nuclear winter, even a one-sided nuclear exchange may have ended humanity.
Well, if the Assured Destruction of causing a humanity-ending nuclear winter with a one-sided strike doesn’t stop a madman from pushing the button, neither will Mutually Assured Destruction.
MAD might have prevented another Hiroshima or Nagasaki. It might have prevented direct conventional warfare between the superpowers, while prolonging the many proxy wars around the globe.
It’s not fuzzy idealism to say that someone has to take the first step rather than further fuel an escalating conflict. That first step doesn’t even need to leave you really vulnerable, it would be enough if it pointed in the right direction.
