Aliens already tried nuclear disarmament in 1987 in Superman IV: The Quest for Peace. The problem, as we saw, occurs when a mad scientist uses the destruction of the nukes as a vehicle to create a nuclear-powered super-villain who then proceeds to wreak havoc on the Statue of Liberty, Great Wall of China and other key landmarks.
We did find out recently that the Aliens would need massive amounts of Coke to get Hillary to "open up"