If I remember her argument correctly, it was that the Japanese government was already trying to discuss terms of surrender with the US for months before the bombs were dropped. They knew the war was not going well for Japan (the understatement of the century, if ever there was one!), that the country was in shambles, their navy and air force destroyed at Midway, their population starving to death, their cities (made of wood and paper still) destroyed by US air raids. The main concern they had as far as conditions went was the safety of the Emperor (something which MacArthur was wise enough to protect after their surrender anyway; perhaps one of the only smart things he ever did in East Asian policy); the main thing holding the Japanese government back from accepting unconditional surrender was the fear that the Emperor would be tried and executed for war crimes and atrocities committed in East Asia. So her arument had more to do with what was going on inside the Japanese government itself, among the decision-makers at the time, according to many archival documents. She really didn't examine popular opinion (I don't think) because it wasn't really relevant to what she was looking at. Even if the average Japanese on the street was brainwashed and willing to fight to the death, it doesn't necessarily translate into the policy of the government; the Emperor and his "advisors" really didn't depend that much on popular approval for their legitimacy (that's why they had the lineage of the Sun Goddess Amaterasu BS). I really do think it would be interesting to compare notes.
Popular opinion isn't irrelevant for many reasons, the least of which is the effect on later relations between the nations. Regardless of the governments plans (or lack thereof, as what is said and what was planning to be done are different depending on who you choose to beleive), the people of the nation would not have given up the war with their nation surrendering. As it stands now, we have a strong relationship with Japan that resulted from a thorough defeat. This is something that I strongly feel would not have happened with a peace treaty.
Furthermore, I think it's completely imperceptive to say that keeping the emperor was the only wise thing MacArthur did. MacArthur's postwar work and the subsequent constitution that was developed set the stage for the country to develop as rapidly as it did, particularly in the technology sector. Of course, I feel rather strongly about this since this was the *exact* topic of my thesis. I'd be happy to send it to you, if you're interested.
In any case, I strongly dislike political debate, because when it comes to politics, there is never a chance of changing the other person's mind. It's like arguing with a wall. (that pertains to me as well, of course!