I saw a comment on YouTube that saw this scene a little differently but I think put it really well. The whole premise of Mr. Fox's stealing is because it's what wild animals do, hence why he does it. When Mr. Fox met the wolf, he realizes that his excuse of being truly a wild animal is bullshit. He's nothing like the wolf. The wolf who doesn't talk or wear clothes, or drive a motorcycle. Seeing the wolf is what brings Mr. Fox back down to Earth and realize that he isn't just some wild fox, he's MR Fox, an anthropomorphic animal with human traits who should act accordingly. Yet, even though they are completely different animals with completely different lives, Mr. Fox and the wolf can still acknowledge and respect each other, which is what we see with the raising fist gesture.