"motivating" ones citizens to fight a war is all well and good, and i'm certainly cynical enough to have no problem with the idea that the spin is being manufactured in any narrative, however allowing the enemy such a massive first strike on your war making ability would be just lunacy. The idea seems more suited to conspiracy and lunatic fringe than reasonable debate.
Yes, I do not think that they did know about the bombing before it happened, but if they did it would be extremely wrong to allow it if they did happened to know about it in advance, just so they could motivate the Americans to go fight them over seas.
The scenario mentioned in the question actually did happen, and it was wrong both in practice hypothetically. It wouldn't have taken much more of the Nazi attacks on neighboring countries to convince the US that its interests were at stake in Europe, but that's speculation since Pearl Harbor actually did happen. The US government allowed the victims of Pearl Harbor to die, even though they didn't know exactly when it would happen, they knew it would happen, and took the cowardly way into the war instead of the noble one.
Yes, it would have been wrong for the US government to allow the Pearl Harbor attack if they knew about it in advance, just to motivate the Americans to fight the war, because the United States should not allow citizens, soldiers or not, to die just to advance a political agenda. If they could have stopped the attack, they should have.
The fact that the United States government was not aware of the Pearl Harbor attacks before hand has not changed. With that being said, I do not believe it would be right for the government to allow any attack to happen that they were aware of simply to motivate American to fight in a war.