It is a persistent myth, and in nearly every diary or front-page story I see here that mentions Hitler, someone will post a comment about Hitler's supposed vegetarianism. I have posted comments in diaries about it before, but I think the debunking needs a wider audience.
For some reason, people also like to drag out this old chestnut in discussions of vegetarianism, as if Hitler's mythical dietary practice somehow infects every vegetarian with a whiff of National Socialism. Why, then, does no one ever point out that Stalin ate meat and killed more of his own compatriots -- perhaps more people in total than died in WW II -- than Hitler ever did?
Now, on to the debunking.
In the real world, not many people would be willing to follow a crude, uneducated little monorchid paper-hanger much of anywhere, no matter how many crazy-sounding manifestos he wrote, unless those people thought the paper-hanger had Something Special. Some otherworldly quality, perhaps, that made him seem as if he were in touch with a Great Unseen Thingy which provided him a Vision regarding where to Lead His People.
In order to make Hitler seem more than he was, then, Joseph Goebbels decided that there needed to be a Hitler Myth...a widespread story about the man which made him seem more ascetic, more heroic, more fit to lead the German people out of the disgrace that the Versailles Treaty had brought upon them. That myth, or at least a big part of it, was that Hitler neither smoked, drank, ate meat, or had relations with women. While Hitler did not smoke, he did drink, he ate meat, and he carried on with Eva Braun.
In fact, turtle soup, stuffed squab, and sausage were among Hitler's favorite dishes. Dione Lucas was a chef at a hotel in Hamburg where Hitler dined fairly often. Of this customer, and her recipe for stuffed squab, Lucas wrote:
I learned this recipe when I worked as a chef before World War II, in one of the large hotels in Hamburg, Germany. I do not mean to spoil your appetite for stuffed squab, but you might be interested to know that it was a great favorite of Mr. Hitler, who dined at the hotel often. Let us not hold that against a fine recipe, though.
So quit catapulting the propaganda. Hitler was not vegetarian.
Sources:
Hitler: The Life and Death of Adolph Hitler by Robert Payne
Why Hitler Was Not a Vegetarian by Rynn Berry
This article on The Food Revolution by John Robbins.