Satan only has as much power over you as you give him. A lot of the theology in Star Wars is nothing more than feel-good pop psychology, but the part where Luke is battling his father and the emperor is spot-on.
A primary trap is to succumb to invitations to hate.
And if Luke was motivated by his hatred of the emperor, he would have gone over to the dark side. But his motivation was to help his father turn to the light side because he still sensed good in him.
Your average church spends all its time fighting evil rather than establishing good, and look where they are. Remember that Darth Vader also started out on a crusade to fight evil.