I just read the following blog excerpt: "Perhaps most unsettling is the manner in which Western observers fail to note what actually motivates Putin and his country. Let there be no mistake, Moscow’s nakedly nationalist chest-beating is widely popular among average Russians; its opponents represent a distinctly minority view that natives will cheerfully explain is foreign-controlled anyway. We hear much happy-talk about the “irrationality” of Kremlin conduct, that such aggression has no place in our current, advanced age, and that it all makes no economic sense anyway. Historians are aware that remarkably similar language was employed by Western pundits and statesmen in the late 1930s to explain away the increasingly aggressive behavior, including cheerful disregard for international norms, by another leader of a resurgent yet recently defeated power."
Did Westerners think Hitler was irrational?
I don't really think there was a consensus at all about what Western leaders thought about Hitler. Take Canadian prime minster William Lyon Mackenzie King, who wrote in his diary after a visit to Berlin
"My sizing up of the man as I sat and talked with him was that he is really one who truly loves his fellow-men, and his country, and would make any sacrifice for their good."
He also wrote that Hitler was "a man of deep sincerity and a genuine patriot" also
"As I talked with him, I could not but think of Joan of Arc. He is distinctly a mystic .... He is a teetotaller and also a vegetarian; is unmarried, abstemist in all his habits and ways."
Now compare that with Winston Churchill who started off somewhat as an optimist but quickly became opposed to Hitler.
"Look back upon the last five years – since, that is to say, Germany began to rearm in earnest and openly to seek revenge ... historians a thousand years hence will still be baffled by the mystery of our affairs"
Pretty much every western leader began to fear Hitler after the Munich crisis because it showed how hungry he was for land. Before that though it varied way too much, some had foresight and saw what he would become, others thought he was just trying to make Germany great again.
Many of the people who visited Hitler were completely taken in. For example the former leader of the British Labour Party and a Christian pacifist, George Lansbury, visited Hitler in 1937 and wrote afterwards:
[Hitler] appeared free of personal ambition...wasn't ashamed of his humble start in life...lived in the country rather than the town...was a bachelor who liked children and old people...and was obviously lonely. I wished that I could have gone to Berchtesgaden and stayed with him for a little while. I felt that Christianity in its purest sense might have had a chance with him.
David Lloyd George, the British Prime Minister during the First World War, visited Hitler in 1936 and he remarked in private to his mistress afterwards that Hitler "is a very great man. "Fuhrer" is the proper name for him, for he is a born leader, yes, and statesman". Shortly afterwards he publicly wrote that Hitler was "the George Washington of Germany":
Whatever one may think of his methods—and they are certainly not those of a Parliamentary country—there can be no doubt that he has achieved a marvellous transformation in the spirit of the people, in their attitude towards each other, and in their social and economic outlook. One man has accomplished this miracle. He is a born leader of men. A magnetic dynamic personality with a single-minded purpose, a resolute will, and a dauntless heart. He is the national Leader. He is also securing them against that constant dread of starvation which is one of the most poignant memories of the last years of the war and the first years of the Peace. The establishment of a German hegemony in Europe which was the aim and dream of the old prewar militarism, is not even on the horizon of Nazism...The Germans have definitely made up their minds never to quarrel with us again.
The prevailing feeling in the West after the First World War was "Never Again" i.e. never again shall there be another war with millions perishing in the trenches. When Hitler told them what they wanted to hear they wanted to believe him because the alternative—another great war—was too terribly for them to contemplate. The ranks of the genuine 'anti-appeasers' was very small.