system
Given the following post, respond as if you're commenting on Reddit:
human
Why didn't Darth Vader let Luke Skywalker strike and kill the emperor, when he met him inside the Death Star?

So, I was watching some video surveillance cameras during my time as a security officer inside the Death Star and I managed to catch a glimpse of the Emperor trying to seduce this guy called Luke into the Dark Side by making him angry.

He was about to kill him when the black guy stopped him from doing this. Why would he do this since if this guy Luke had killed the emperor he would have joined the Dark Side and ruled the galaxy with Darth at his side? He even said so right after this happened!

Luckily I managed to escape and now I'm asking what the hell was the robot guy thinking?
gpt
That's "Lord Vader" to you. Luke was the subject of a very complicated recruiting attempt. The empire was offering him more than his terrorist friends, but to do that he must pass a test, that test was allowing his anger to control his actions. 

Lord Vader was once a Jedi of the Republic, but he couldn't bare to see his son turn as he did. Had Luke shown more flexibility towards joining his father, Lord Vader may have let him kill the emperor, but instead of allowing it to happen, he disguised saving his son as loyalty to the emperor. Had Luke killed the emperor his fate would have been sealed. Instead it lead to Lord Vader's final redemption, and he, killed the emperor but a short time later. 

Also, how the eff did you get off the Deathstar?!