I agree that cheating isn’t the worst thing someone can do. There may be moments when it can be understandable, but in the majority of cases when the person cheating does it solely for their pleasure, they show that they are extremely selfish and need to face consequences. Imagine if your wife cheated on you, but all of your friends acted like it wasn’t a big deal and didn’t care that she could hurt something like that. I am also wondering why you thing this is the one thing they can that doesn’t affect you personally. Earlier you dismissed OP’s argument about being friends with a wife beater or a child molester, but this shows that there needs to be a line drawn somewhere of what someone can do that doesn’t affect you personally, but would still affect your relationships. Yes, cheating is not as bad as those things, but if someone does something to knowingly hurt others, especially the ones closest to them, for their own momentary pleasure it should affect your relationship, or at least they eat you think of them