Something just occured to me, considering the generally bad treatment of robots in the Star Wars Universe, where ones that appear to be sentient like C3PO and co are freely bought and sold, could the repeated use of the description "he's now more machine than man" people use regarding Vader be implicitly derogatory?
As if him being a child murdering fascist wasn't enough, they had to reference his "otherness" as well or something to dehumanise him, though in... I guess for a Science Fiction universe, kind of racist/speciesist(?) terms.