I can wonder how many lines just ahead might be called on in order (and I'm thinking a bit of the book "Star Wars: The Magic of Myth," which looks at them as various "temptations" for Luke). As for this one, though, it is useful to have it be pointed out as more "words of an abuser"; given the resolution to come one movie from now, I can see a certain risk in trying to find some "sign he's not all evil" even here. (So far as Luke having to face some blame, though, his trying to pursue Vader out of the carbon freezing chamber rather than chalking a narrow escape up to experience and making a getaway does seem significant.)

One thing I did get to thinking was that the young Darth Vader (back when "Anakin" might seem still applicable to him too) makes a similar "Don't make me kill you" threat to Obi-Wan in Revenge of the Sith. Maybe there the temptation's to say something about "in what circumstances (quite possibly 'outside the story') is the word 'kill' avoided?"