A nuclear attack no matter how small will have as much a
psychological effect as it will physical. If a few airplanes using
just jet fuel killing "just" a few thousand people could have such
ramifications beyond the physical damage, imagine what a small
nuclear attack will do.

And what's to keep a small nuclear war from escalating into a
big one, the kind that sends us all back to the stone age, if
we're lucky?

Do you think "just" 50 warheads between two neighboring nations
isn't going to have maybe a slight effect on them if they use even
half that number? Edward Teller would tell you that one doesn't
need to wipe out everything to wreck civilization, just take out
the cities.