Final answer:
Roosevelt's "Day of Infamy" speech conveyed anger at Japan for their deceit and surprise attack on Pearl Harbor, which supported America's justified participation in World War II.
Step-by-step explanation:
The best-supported inference about Roosevelt's point of view in his "Day of Infamy" speech is that he is angry at Japan for deceiving the United States and attacking without warning. In his speech, Roosevelt highlighted the secret and calculated nature of the attack using a strong rhetorical strategy, referring to the event as a "date which will live in infamy." The tone of his address and the historical context suggest that while Roosevelt had been foreseeing potential conflicts and assisting allies, he did not predict the attack on Pearl Harbor nor did he have an immediate desire for revenge on the Japanese people. Instead, Roosevelt's focus on the suddenness and deceitful aspect of the attack supports the inference that he was incensed by the lack of forewarning and the sneak attack nature of Japan's actions.