There is a lot of questionable aspects about this alien invasion story that I don't buy, but thankfully Zach, our protagonist, is questioning everything that doesn't make sense. Humans suck. Of course they could be making this up and it's really us doing the attacking. Too bad he's straight up being manipulated to enlist right now.
But something that's niggling at me, granted it's very minor but bear with me, is the idea that Star Wars was an anti-alien propaganda film. To us Earthlings everyone in that movie was an alien. The primary conflict wasn't between alien species anyway, but between the Sith and Jedi — multi-alien species groups using different sides of The Force.
So, it seems to me that as propaganda that film fails big-time.
P.S. - Safari spellcheck recognizes Jedi but does not recognize Sith. Rude.