Dude it would have been so cool if the show went over galra propaganda. I actually have two ideas of what sort of justification the empire has for the destruction they cause.
1) Daibazaal is gone, and taking revenge for it’s destruction was what started the empire’s war path. Therefore they justify their conquering of worlds by saying “they took our home, so it’s only fair we take theirs”
2) Zarkon was the original Black Paladin. The other paladins going against him and hiding the lions is probably framed as mutiny by jealous teammates, and Zarkon’s actions and decisions are framed as the correct decisions as he was chosen by the Black lion to lead Voltron. When the new paladins enter the scene, they are likely labeled false paladins who tricked the lions into letting them pilot them.
