It can be so hard for a couple to stay together when one of them cheats, not because of the reasons you might think, but because there is so much social pressure to break up. If you don’t break up, you are seen as a loser with no self-respect. We see that in some of the comments above.
What most people don’t understand is the complexity of relationships and that some people can get past the pain of infidelity and rebuild a decent relationship. Sure, in many cases, the mistrust makes any further relationship pretty much impossible. But in most cases, this does not have to be the death knell.
Relationships are about more than pride. Most people see pride as something like self-respect—aka, not letting yourself be walked over. Pride gets in the way of a lot of problem solving—relationships or nations or in any other kind of negotiation. We have this idea about what is fair and just. “It’s not fair!” We complain all the time.
Life isn’t fair, and the sooner we accept that, the sooner we can get past situations where we let our wounded pride keep us from letting some things go so that we can get other, better things.
Infidelity is not necessarily a callous slap in the face. In fact, it really isn’t about you at all. It’s about the unfaithful person and the issues they are dealing with. Now you can tell them to fuck off and deal with their issues on their own time if you want. Or, if you love them and see much of value in them and in your relationship, you can buckle down and work to save the thing.
Couples counseling with a good counselor really can help. Opening up communication so you can share your inner pain helps. You have to air out the dirty laundry—that is, raise all the secret issues—and then, maybe, you can make it so you are both happier.
Infidelity is really less than people make it out to be. Rarely does it mean much to the person who is doing it. It’s more acting out because they don’t know what else to do with their pain. They think maybe someone else will save them, but that’s pretty much never the case.
Listen to your friend. Support him in doing what he wants. Please don’t get in his face about this. Rein back your “protective” feelings. Be there. Listen. Help. Don’t give him unwanted advice.