Frank, your friends have never been in your shoes.
I confess my whole morals changed since I found out about H's escapades. I used to be like your friends: a guy cheats on you, even once, he is out!! However, once you are actually living it, it's not so easy. Few people in this planet cheat just out of boredom or because they want variety. There is usually a WHOLE lot more missing in the current R and we instinctively know this.
Not defending our Ss, here, mind you. I am just validating your position. Only you know what happened between you and your S. Not even we here at BB are entitled to push you one way or another. Dealing w/ betrayal + attachment is confusing enough.
