I think that Loki is tired. Hes exhausted himself for who knows how long trying to gain Odins acceptance, to get Odin to understand why he did what he did. Now hes 110% done. Im so glad they put this scene in the movie. It wasnt in the film originally, but Tom Hiddleston pitched it to the studio. He said that the audience needed to see Lokis trial and punishment, to see what had happened to the character. So when they did re-shoots they used Toms idea. Stroke of genius.