Originally Answered: Why did Jehovah's Witnesses side with Hitler and the Nazi's in the 1934 Yearbook of Jehovah's Witnesses?
Supporters of religions which were blatantly guilty of supporting Hitler desperately attempt to twist the facts regarding Witnesses' actions. Especially do they do this by ripping what the JWs really said out of context and misrepresenting it. The context is that JWs support the principles of justice underlying the laws of many governments --such as the US Constitution. But, we do not support it when political factions such as Hitler's pervert those principles.
But you don't have to take Witnesses' word that these people are twisting the facts. Here's a quote from a non-Witness Holocaust scholar who examined all the facts regarding the 1933/34 resolution and letter:
"When the entire text of the Declaration of 25 June 1933 and the letter to Hitler are seen today in the context of the history of Jehovah's Witnesses during the period of National Socialism in Germany and the history of their religious resistance and their stand during the Holocaust, then the text does not present itself as an "antisemitic statement" or an attempt at "currying the favor" of Hitler. THESE ACCUSATIONS, STEMMING FROM PRESENT-DAY CHURCH CIRCLES, ARE DELIBERATE MANIPULATIONS AND FALSIFICATIONS OF HISTORY, SEEMINGLY MOTIVATED BY GUILT OVER THE CHURCHES' OWN INVOLVEMENT or lack or involvement in the persecutions."--Spiritual Resistance of Christian Conviction in Nazi Germany: The Case of the Jehovah's Witnesses, By Gabriele Yonan, Journal of Church and State
Further, just look at the opening statement of Rutherford's letter:
"This letter is both a friendly notification and a warning about things that will be of the utmost importance for your well-being...The warning goes out that all those who stand up against God and his Kingdom will be destroyed by the Lord in Armageddon. Your government has disregarded this warning."
As noted by Gabriele Yonan, upon reading the Declaration Hitler exclaimed: "This brood must be exterminated from Germany."
In her book Dr. Christine King concludes: "Only against the Witnesses was the government unsuccessful...The work [of preaching] went on and in 1945 the Jehovah's Witness movement was still alive, whilst National Socialism was not." She also points out: "NO COMPROMISES HAD BEEN MADE." (The Nazi State and the New Religions: Five Case Studies in Non-Conformity)
Any claims that Witnesses supported Hitler's racism toward Jews is disproved by the facts. Notice some comments published in Judaism Today, Winter 1999-2000: "The tenets of the Witness faith represent a sharp departure from traditional 'Christian' antisemitism. Witness belief is characterized by a resolute belief in the brotherhood of man reminiscent of first-century Christianity. Notes historian John Weiss, 'The Witnesses were free of German racial nationalism.'...Their principled aversion to racism in general motivated their specific rejection of Nazi and church- inspired antisemitism."
Now, does that sound like Rutherford and the resolution were supporting Hitler? So those who misrepresent what the resolution and letter actually stated are deliberately misrepresenting history.
The following links will take you to an HONEST evaluation by non-Witness scholars"
One very good book is "The German Churches under Hitler" by Ernst Christian Helmreich, Wayne State University Press, 1979
It chronicles in detail EVERY religion in Germany at the time. Here are some excerpts to support what has been said in answers here.
"The Jehovah's Witnesses...were treated the most severely. They were given short shrift and no one spoke up in their behalf." ;287
"Witnesses never gave up bearing witness according to their concepts. The police summary of events of 1938 laments that in spite of orders for their dissolution, Jehovah's witnesses continued their activity." ;396
"the record shows that the Witnesses held true to their convictions. No one knows for certain, but it has been estimated that one to five thousand lost their lives in prison and concentration camps...They never ceased to carry on their missionary work, and their "witnessing" even brought conversions within the camp.". ;397
"Hitler, was brought up in the Catholic faith and until his death was never excommunicated from the church, listing himself to the very end in the party handbook as a Catholic." ;123
"Both Catholic and Protestant clergy did their duty to the state as they had done in past wars; there were no conscientious objectors." ;355
Clear statements by non-Witnesses scholars prove that the Witnesses were the ONLY ones who officially as a group refused to support Hitler.