Answer: He wanted to convince Americans that war was the only way to deal with Japan.
Explanation:
President Roosevelt is using strong language here because he wants to convince Americans that there was no other way to deal with Japanese aggression than to go to war with them.
He implied that peaceful negotiations could no longer occur on account of the Japanese having attacked the United States on Sunday, December 7, 1941, by bombing Pearl Harbor in Hawaii and killing both military and civilians and that war was the only way to reply such aggression.