I'm guessing you might have latched onto:

Ferguson’s best passages are his damning but entertaining narration of the naïve, self-regarding and sinister folly of Anglo-French appeasement: “Our enemies are little worms,” Hitler said. “I saw them at Munich.” Ferguson argues that the Western powers should have gone to war in 1938, which would most likely have avoided much of the horror of World War II, or Britain and France could have forged an alliance with Stalin as a deterrent.

But I can't turn a blind eye to the rest of the paragraph:

He is undoubtedly correct, but this is simply omniscient hindsight: at the time, Stalin probably regarded the West as his chief enemy, while many in the West regarded barbaric Bolshevism as theirs. Moreover, it’s questionable if public opinion would really have tolerated war in 1938. Still, Ferguson is certainly right that “Stalin’s policy of trusting Hitler was a calamitous blunder without equal in the history of the 20th century.”

I think that "what ifs" are up against the reality of the people and ideologies involved, their long histories of mutual distrust and antagonism, and so on. It's not just one decision, such as Chamberlain's overtures to Germany, that would have to be different to have made things turn out differently. Rather, all the decisions of several hundred years of European history that set up the situation that gave rise to Hitler and the conditioned responses of everyone else would have to have been different.

There are, of course, many times when appeasement is the wrong move, at least in hindsight. But sometimes reality requires accommodation. One could label our present policy toward Iran and North Korea as somewhere just short of appeasement; it's definitely not the strong and violent action that hawks would like. But do we have a choice? If we wanted to attack Iran or NK, where would we find the army to do so? Maybe we could pull it off with a genuine coalition to make up the shortfall, but then the hawks would scream about "appeasing" the UN and France and Germany. Cold calculation might conclude that flattening Iran is necessary, but reality says we don't have the means to do so with the resources and geopolitical players, and their ideologies and self-interests, at hand.

It's inevitable that if Democrats succeed in forcing a redeployment of US forces currently pinned down in Iraq, our position will be strengthened when it comes to dealing with other problems like Iran and NK. As it is, they all know we can't back up any threats we make, and the continued defiance shows their calculation of our position right now. Even if one thinks that invading Iraq was a good idea in the first place, I don't see how anybody can find anything positive in the way we've been bogged down there ever since. We have to get out of Iraq while we still have some strength left to take on new adversaries; we dare not risk bleeding-out in Iraq.