I agree, that's the first time I've heard that (pretty interesting) argument made, and it sounds reasonable. However, it seems more like propaganda working too well, to the point of affecting the country's modern day leaders.
A couple points:
You can't say that you're freeing people from imperialism if you're just going to occupy them immediately after ousting the previous occupiers. It also doesn't help if you treat the occupied people vastly worst than before. However, the national mentality regarding all this makes perfect sense if you consider what would have been reported on back home during WWII. Japan wins many battles all over Asia, ousting Allied and White influence. Japan is helping develop the region by building a significant amount of infrastructure including railways, power plants, housing, etc. (There's a joke in China that says that any building still standing since 50 years ago is guaranteed to be of Japanese construction; their building standards were of very high quality, especially compared to crappy Chinese standards). Japan is spreading culture and enlightenment to an inferior people, who are benefiting from our intervention. What nobody hears about are the war crimes, mass civilian murder during occupation (people promised wages and housing to work on various projects, later killed without pay to save on expenses), human experimentation (unit 731), forced prostitution (comfort women), torture, slavery, etc.
Now consider that Japan's censorship was (is?) pretty effective regarding WWII history if you look at their curriculum. People growing up there likely didn't know much about many of the war crimes that occurred, and to some extent might think that the rest of Asia is slandering them. At least, they don't believe enough of it to remove shrines celebrating war criminals, or abstain from saying stuff that pisses off the rest of Asia.