Obama approvingly quoted Reagan in a recent speech to the UN:
"A nuclear war cannot be won and must never be fought. And no matter how great the obstacles may seem, we must never stop our efforts to reduce the weapons of war. We must never stop until all -- we must never stop at all until we see the day when nuclear arms have been banished from the face of the Earth."
Well, we live in a different world now. It is most certainly possible to win a nuclear war against virtually any nation on the planet, just not Russia, and probably not a good idea to pick a fight with China. Disarmament only works when other parties reciprocate. I don't see North Korea (or China, for that matter) disarming, nor Iran stopping its nuclear program.
The structure of the nuclear game has changed, and not all of the players are rational actors. Quoting Reagan in this context is naive and dishonest.