I'd tell my friend that his cheating is a deal breaker and we are no longer friends for as long as it continues. Then he'd be gone as a friend. Any future activities would be invite only to the wife. That likely will tell without telling.
Let's say you have a married couple whom you are close friends with both but one of them is cheating. Do you tell the other person that they're cheating or do you mind your business because it's not your marriage? What would you do in this situation?
My old boss used to say "I only have 3 friends and don't like 2 of them".Another tremendous reason to not have friends...
I got this covered.I would do the SGT Schultz routine.