Imperfected
Member
Look, Bucky wasn't responsible for the death of the Stark parents, but you've got to read the room and prostrate yourself in apology anyway. Not doing so almost cost Bucky his life. Everyone in the thread is giving great explanations of the situation. Bucky should have tried one. Instead, his silence essentially tells Tony "deal with it, idiot."
That's reasonable, but again, Bucky is a severely damaged individual.
They actually set up for this with the "Manchurian Candidate" scene immediately beforehand: Bucky has no ability to read social situations anymore. He literally cannot read the interplay between Steve and Tony until both of them spell it out for him what's going on.
He probably spent the entire fight just trying to process what's going on. The only reason he's even fighting back is probably raw instinct.