Actually if you follow the historical timeline of the events, the Japanese and American diplomats were in the middle of peace talks at the time. Japan had intimated that they were not looking to take any American territories, unlike what they had already done with the western Pacific rim and parts of China. Unfortunately, we did not know they were as close as they were due to the cut backs in the National Defense budget.
The Japanese Ambassador in Washington was suppose to hand the Declaration of War to our Secretary of Defense, 30 min. prior to the attack. There was a problem with the decoding of the order from Japan to the Japanese Ambassador which set the time of declaring war on us not until after the attack already happened.
That is why it has been looked down upon, because war had not been declared by either side, and the Japanese had been actually talking peace rather than what took months of planning.