Yes, I agree with this overall point. Hitler and his Nazis were the symptom of the problem, the main problem was virulent anti-democratic nationalist influence which allowed a person like him and his organization to ascend to power and then rule the country which never really was that much into them in the first place.
And this anti-democratic feeling in Germany was fueled by the first great mistakes the Allies made, and that was on 11 November 1918. When the German army command sued for an armistice, the Allies allowed it to be signed in German side by a MP, the catholic Centre party member Matthias Erzberger, and not by the military. German supreme commander Hindenburg and his chief of staff Ludendorff should have done that; armistices aren't signed by civilians but by military. This crucial piece allowed that piece-of-work Ludendoff, who later was Hitler's co-conspirator in the Beer Hall Putsch, to perpetrate the stab-in-the-back legend: the army had been undefeated in the field, it was those pesky democratic politicians which had lost the war for Germany.
And to top it off, the Allies should have held a victory parade on the Kudamm.
On its own, the Versailles Treaty was not that harsh: it was milder than the 1871 Treaty of Frankfurt, which in turn referred in its amount of indemnities to the 1806 Treaty of Tilsit, in previous Franco-German wars. Also, the much-maligned "war guilt clause" is a red herring: It was a standard clause about Germany's responsibility for indemnifying the victors, and the same clause appeared in the peace treaties with Austria, Hungary, Bulgaria and Turkey, and none of those countries ever whined about that they got stuck up with admitting guilt of starting the war.
And on top of that, the democratic government in Germany decided to spite its face by cutting of its nose with an unnecessary hyperinflation in 1923, and blamed it all on "Versailles". And the Allies fell for it all hook, line and sinker. But by the time that Hitler came to power, the Versailles payments had all been stopped for a few years already.
Of course, that is all hindsight and all, but it still strikes me as unreal that the Allies let a civilian sign an armistice, and then let the chief of staff who begged for that armistice run for years a slander campaign that his army had not been defeated in the field.
And maybe Germany was simply still not up for truly democratic governance. The whole bureaucracy, judiciary and all educators were still deeply steeped in the aristocratic class society of Wilhelminian Germany. If there's one thing we can thank Hitler, as well as Stauffenberg, for, then it's the elimination of the German nobility, in particular the Prussian junkers.
