Nuking Moscow would have forever repudiated the idea that America stood for justice and righteousness and that we could be trusted.
By doing so we would have turned on an ally which had already lost 24,000,000 dead in WWII vs our loss of 600,000 lives in the war.
And this is the position the Leftists in America are now in.
They have chosen to turn on the Right and make us their enemy and they can't turn back and now they HAVE to defeat us or eliminate us.
And they will always be known as traitors and sneaky, deceitful, untrustworthy bastards.
The idea of nuking Moscow is a short sighted, sophomoric move that, once done, quickly becomes apparent was the worst thing we could have done.