Panel 1: Since John lives in fear of her reaction to being found liable for a moving violation, he asks Elly if she's really going to fight her ticket in traffic court. As she folds some shirts, she answers him by telling them that the hearing is next week.
Panel 2: John sets up the punchline by asking her for sake of argument, what happens if she doesn't win. She bluntly states that then, she loses.
Panel 3: Since he still fears having to deal with her losing the court fight, he asks her why she's going through with this if she isn't sure she's going to win.
Panel 4: When she repeats back his "For the sake of argument", he's rather baffled.
Summary: He shouldn't be. He's been married to her for fifteen years or more and should know that her worst fear is being some mute little dummy who isn't allowed to talk or have an opinion. I see crap like this and I start to wonder if he knows her at all.