I mean that Christianity had been planning the Holocaust for hundreds of years
Let's look at some actual Nazi propaganda, shall we?
This is an official NSDAP propaganda issued by Alfred Rosenberg’s office in February 1944.
https://research.calvin.edu/german-propaganda-archive/weltparasit.htm
"At the beginning of the war’s sixth year, we may not permit ourselves to neglect the Jewish question in any way.
First of all, we must always combat the remnants of past education, the once general view in which Jewry is seen only as a religious denomination. Instead, the racial mixture that is Jewry must be emphasized.
The religious beliefs of the Jews are completely irrelevant. Instead, we must focus solely on blood, on the racial foundation.
From the beginning of its existence, the National Socialist German Workers’ Party has always attempted to educate the German people about these facts. As early as 1922 the Führer said: “We were also those who for the first time made major efforts to explain to the people a danger that had crept up on us, and which millions of people did not recognize, even though it threatened to ruin us all: the danger of the Jews.” In his book
Mein Kampf (p. 335), he said: “Over the long term, he can preserve his existence within other peoples only if he succeeds in persuading them that he is not a people, but only a ‘religious community,’ albeit a peculiar one.”
The first and greatest lie, that Jewry is not a racial question, but a religion, inevitably leads to further lies. Another lie concerns the Jew’s language. It is not a way for him to express his thoughts, but rather a means to conceal them. Although he may speak German, French, or some other language, he thinks in a Jewish way. He may spout German poetry, but he remains a member of his race. Heinrich Heine is the best example."
Or this from a 1939 citizen's pamphlet:
https://research.calvin.edu/german-propaganda-archive/imbild1.htm
"Greater Germany is the first country in the world to find a legal way to separate from the alien Jewish people. In contrast to the views of the last century and of the so-called democrats of today,
National Socialism sees the Jewish Question not as a religious problem, but rather as a racial question."
This is from a 1936 pamphlet on how to resolve arguments from non-antisemites:
https://research.calvin.edu/german-propaganda-archive/responses.htm
"Argument 1: “You say that religion is a private matter. But you fight against the Jewish religion!”
Counterargument: “Actually, the Jewish religion is nothing other than a doctrine to preserve the Jewish race.” (Adolf Hitler). “In resisting all government attempts to nationalize them, the Jews build a state within the state (Count Helmuth von Moltke). “
To call this state a ‘religion’ was one of the cleverest tricks ever invented.” (Adolf Hitler).
“From this first lie that Jewry is a religion, not a race, further lies inevitably follow.” (Adolf Hitler)."
Your theory also fails on the grounds that the Nazis also killed Jewish converts to Christianity if they had two or more Jewish grandparents.
