Yeah, I get you.
I know that if I was being cheated on I would want to know. I would hope my friend to tell me.
I know it would be painful for my friend to tell me and I would be hurt deeply, by the cheating but I would want to know.
I dont think the relationship with my friend would be hurt. I know my friends have my best interest at heart

Finding out lets the couple work on the problems on what led to the cheater cheating and the reasons why. They could then work on their marriage and decide what would be the next step. Could go bad, could go good.

I would want to know.