Why is it better for a nation to be nuked than turn Communist?

Nixon considered using nukes on Vietnam, Truman considered using them on Korea. And we all know about the Cuban Missile Crisis. Is it not instructive to know that US foreign policy is so dedicated to getting the 'last word' that they will consider the use of nuclear weapons to get their way? If you were a citizen of Korea or Vietnam would you prefer to be ruled by Communists, or flash fried in the name of 'freedom'?