Are there any in-universe justifications for why Sabine Wren and Zeb Orrelios spared Rukh in the episode DUME? The rebels have demonstrated that they have no problem killing imperial agents like Stormtroopers, so why not an imperial assassin? He has been a constant threat to them, especially since he out-fought and then captured in the episode Rebel Assault, so why just let him go?
He is a valuable imperial agent with very advanced tech, so why just send him back to the enemy? Even if they weren’t willing to kill someone outside of combat (despite him being an assassin), imprisoning him so he can’t go back to working against them is only good sense. Also, interrogating could have led to valuable insight into how Thawn and Price’s operation on Lothal was set up. At a minimum they should have stripped him of his gear and contacted Hera for orders instead of sending him back to the empire in an attempt to humiliate him.
To be clear, I am looking for something more substantial than “the writers wanted him around for the final battle.” Are there any explanations for why two skilled, successful rebels, would ever make such a poor decision that could have led to the deaths of their friends and themselves?