Hitler gave lip service to Christianity; his real religion was evolutionism as I've noted and as Sir Arthur Keith described.
Yeah, right. He was a baptized Catholic, he asked for and drew support from Christians, he made statements that he was doing God's work; and the Holocaust he brought about was just the last in a long series of mass extermination attempts against the Jews conducted by European Christians, starting in the Middle Ages, continuing with the Spanish Inquisition, Martin Luther's tirades the Jews, the pogroms of central and Eastern Europe, etc.
But despite the open admissions of the man who instituted it, and the long historical trend it continued, it was a scientific theory that caused Nazi-ism and the Holocaust.
Some links:
Hitler appeals for support from his fellow Catholics.
This link has some nice quotes from Mein Kampf.
"Hence today I believe that I am acting in accordance with the will of the Almighty Creator: by defending myself against the Jew, I am fighting for the work of the Lord.""My feelings as a Christian points me to my Lord and Savior as a fighter. It points me to the man who once in loneliness, surrounded by a few followers, recognized these Jews for what they were and summoned men to fight against them and who, God's truth! was greatest not as a sufferer but as a fighter. In boundless love as a Christian and as a man I read through the passage which tells us how the Lord at last rose in His might and seized the scourge to drive out of the Temple the brood of vipers and adders. How terrific was His fight for the world against the Jewish poison. To-day, after two thousand years, with deepest emotion I recognize more profoundly than ever before the fact that it was for this that He had to shed His blood upon the Cross. As a Christian I have no duty to allow myself to be cheated, but I have the duty to be a fighter for truth and justice... And if there is anything which could demonstrate that we are acting rightly it is the distress that daily grows. For as a Christian I have also a duty to my own people.
-Adolf Hitler, in a speech on 12 April 1922 (Norman H. Baynes, ed. The Speeches of Adolf Hitler, April 1922-August 1939, Vol. 1 of 2, pp. 19-20, Oxford University Press, 1942)
(Cited in the above link)
The anti-Semitism of the new movement [Christian Social movement] was based on religious ideas instead of racial knowledge.
- Mein Kampf, ibid.
As a general account of why and how Germans participated in the Holocaust, and how it fit into the (stongly Christian) German cultural tradition, I recommend Goldhagen's "Hitler's Willing Executioners".