Actually, given the possibility of global nuclear winter, even a one-sided nuclear exchange may have ended humanity. So in that case, mutually assured destruction during the Cold War may actually have saved humanity even if one side got in a successful first strike and wasn’t hit itself. But that’s obviously not the point. What I’m objecting to is the fuzzy idealism that says in a multi-sided situation that one side should give up its tools (weapons or intelligence) unilaterally, trusting other sides not to take advantage of the situation.
