Regarding atrocities, you clearly have no idea how deeply the wartime atrocities impacted many Asian families. Many Korean families I know refuse to buy Japanese cars or products (my mom is Japanese, so I've been told this many many times). My Korean father-in-law was an orphan because of the Japanese occupation.
In any case, the above fails the first rule of jokes... they're supposed to be funny. I thought the post was funny enough. But the reference to a co-prosperity system didn't add much (any?) humor to it. Just pointing that out to the OP...
The anti-Japanese grudge does run fairly deep, but as far as I can see it seems to be slowing significantly in younger people. The parents of people I went to school with (graduated university 2010) might hold one, but my friends are much more moderate.
Personally I thought the co-prosperity added to the humour with an over-the-top name, and I detected a slight whiff of Eastern Bloc over-the-top naming, akin to Council for Mutual Economic Assistance or Polish–Soviet Friendship Society. But then my ethnic background is Polish and not an East/Southeast Asian one.
That's not the 1st rule of jokes! The 1st rule of jokes is that there are no rules. The 2nd rule of jokes is that everyone finds different things funny. The 3rd rule is to break all the rules.
Repurposing the stilted propaganda of long-ago times, or of clumsy tyrants, for subtly absurdist/ironic humor value, does not in any way lessen the original horrors. It celebrates the distance we've achieved, while also offering a teaching moment by contrast/reference.
See also: "we will bury you", "let a thousand flowers bloom", "we had to destroy the village in order to save it", "i have in my hands a list of hundreds of known Communists", "the war to end all wars", "the mother of all battles", "this blogger has been harmonized", etc.