As we all know, John could have avoided the predicament he got in when he hired a new hygienist if he weren't as stupid as a sack of hammers. After all, an observant human being would have picked up on his wife's insecurities about her looks and fears of his cheating on her long ago. Not John. Instead of doing what insanitypepper said and saying that both candidates are equally qualified, he witlessly brings the irrelevant topic of looks into the discussion. He further screws up by suggestion that Elly's lost hers. What's more, despite his being told to his face that she's always been afraid that he'd cheat, he refuses to admit to himself that she has a legitimate reason to panic. This is because he is not only a brash, arrogant douche, he's also a goober. Throughout the run of the strip, he was portrayed as being too dumb to live. It would seem that Lynn ascribes Rod's habit of doing things that infuriated her, borne of her own refusal to tell him out loud that she had issues with him, to his being an imbecile.