I think the most likely reason Churchill regularly brougth up negative details about the war is:
A. He wants Britain to have realistic expectations about the future.
As a great strategist, Churchill focused on the evidence given by other battles, like the German victory in France, to learn from his enemy. By lying to his people, british army would not be prepared for the battles coming and wold be defeated. Some generals in World War II believed that war would be fougth like World War I, they were not based on any evidence, and were eventually surprised by the new tactics the German developed (like the Blitzkrieg).
Churchill was able to make alliances with the United States and the URSS, so letter B. seems incorrect.
History made clear that Churchill was a great leader that never gave up so letter C. seems incorrect too.
By giving negative details abaout war Germany wouldn't think Britain is weak so letter D is incorrect.
