I got no idea what the context for that is, but I do know that Japan has a problem with right-wing revisionists who think that Imperial Japan did nothing wrong. It seems to be sourced basically from the fact that Japan never went through the process of "de-Nazification" that Germany did, with the result that modern Germans have a very clear and honest grasp of their country's unsavory history, but modern Japanese are not likely to even be aware of shit like Nanking. Schools just don't address the topic; students have to go find out about it on their own, and some of them slip into denial as a result.
Because people make anime and people are political, that thread sometimes appears in anime to a greater or lesser extent. Code Geass, for example, while being a pretty great show, had the uncomfortable premise of a formerly-independent Japan being conquered, subjugated and exploited by a fantastical stand-in for the USA blended with British imperialism. High School of the Dead, apart from the gun porn and...well, the regular porn, had a right-wing militia show up in the latter part of the season as the good guys. Which was weird, to be honest.
I mean, it never felt too blatant to me and I was often told I was reading too much into things, and I can accept that. But I feel that once you start thinking about it, you keep seeing this strong revisionist undercurrent running through Japanese media, tying anti-Americanism and the bombing of Hiroshima and Nagasaki with denial of Imperial Japanese war crimes committed in the 30s and 40s. I don't even think it's intentional or malevolent; the Japanese just get taught "America nuked us, twice, and then we surrendered, but it's okay now," and no-one mentions all the parts about the rape camps and inhumane scientific experiments. I can't even blame them; sometimes, the history of Imperial Japan seems too cartoonishly evil to be real.