A lot of people are holding onto the idea that the only reason he'd take the other woman's side is if she is an old fling or cheat partner etc. A husband can take a side against his wife just if there's trouble between them that has nothing to do with outsiders. My husband is an emotionally abusive asshole who criticises and demeans me every day. He almost always disagrees with me and takes the opposite side of whatever I'm involved in. If the husband in this story thinks his wife is immature or disagrees with whatever relationship advice she was giving, or if he feels like she embarrassed him, He could take the other side just because he doesn't like his wife's behavior.