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.