Your reaction is more interesting than your father's. To an outsider, the epic scale of your emotional response is curious. I could see a response of disappointment, or sadness, or eye-rolling at the sheer stupidity of someone keeping a catalog of one's marital crimes in the bedroom. But massive rage that goes on for many years? I have to ask, why? It's their marriage, not yours. One thing I've learned over a long life is that nobody, not even the people involved, ever understands a marriage. People barely understand themselves, almost never understand other people, and will never get to the bottom of the emotional complexities between two people sharing a life. I've never understood why even the parties involved invest the actual adulterous act with such importance. It's painful, but, in my experience, it's almost always a manifestation of deeper issues, often issues that have little to do with the marriage. A spouse having an affair is a big deal--nobody likes it--but to make it the center of two people's future life permanently is absurd. Absurd because it's one of two things: the adultery either has little to do with the injured party, in which case a huge reaction isn't warranted, or it does have to do with the injured party, and it's a symptom of a deeper flaw in the relationship. The actual f'ing around isn't the real problem. But in either case, how can it make sense that something that happens between two other people can support huge emotions in a third party that go on for years unless there is something personal fueling it? We're all fools who do stupid shit all the time.