So Son'a are Ba'ku.
This revelation basically killed any chance this movie had of working for me.
At first it seems like the Son'a are aliens looking to forcibly steal the Ba'ku's home world. But since the Son'a are in fact Ba'ku, I'm not even sure who's bad guys here.
Basically, the Baku kicked the Son'a off the planet for not embracing their ultra-luddite philosophy, and now that the Son'a need to come home to avoid dying of old age, the Baku won't hear of it even though there seems to be enough room on the planet for everyone.
Given that they were going to be able to move the Ba'ku to another world with one spaceship that was small enough to fit in a lake, the Ba'ku seem like religious zealots who want to force everyone else in their race to adopt the same lifestyle they do, and the worst land Barons in history claiming ownership over all the land on an entire planet when their cannot be over a few hundred of them.