I find it baffling that you can speak about open conflict between two nuclear superpowers so confidently. Nuclear exchange would mean, best case, collapse of c

I find it baffling that you can speak about open conflict between two nuclear superpowers so confidently. Nuclear exchange would mean, best case, collapse of civilization with a possible extreme worst case of human extinction. Why in God's name would you even tamper with the possibility? Or do you think that nukes would never be used, no matter how desperate either side got?