First, I'm talking about maybe 50 years ago. Second, I never said it was legal.
This article explains it better than I can.
Rauch was wrong on this point. Custom dictates that the community look the other way about adulterous behavior when it is possible to do so. Discretion when committing adultery is not just a way to hide your behavior; it is a courtesy to everyone, most especially your spouse. But this is not a blanket social writ to go around cheating on the spouse. If you are caught, exposed, or simply so wantonly flagrant in your behavior that your behavior can no longer be ignored — or, in Bill Clinton's case, all three — then society must judge.
The same holds true when cops are caught on aerial cameras beating someone in broad daylight or, for that matter, when evil doctors like Jack Kevorkian (abetted by CBS) are seen on network television killing a patient. Such exposure forces the issue into the public square, because nobody can convincingly pretend it didn't happen, and legal norms and social fictions must be upheld. Such exposure often makes prosecutions unavoidable and some unlucky bastards often pay an unfair price. But just as we can pretend, up until a point, that doctors don't kill patients, or that your neighbor or your president isn't a cheating bastard, when the issue is spilled into your living room, we must disapprove. Such hypocrisies are some of the small payments we make for civilization.
Michael isn't discreetly trying to honor his wife's wishes (which just happen to be illegal). He's blatantly abusing and murdering her, while rubbing everyone's face in it. I am not capable of pretending he isn't doing it. I am not capable of pretending it's right. I don't understand anyone who is, and I don't want to. I don't ever want to become so detached from humanity that I can understand that perspective.