This^^^^. Yep been down that road myself. That's why when it comes to relationships I don't say squat. My Business partner told me a week ago he was leaving his BF. He then went on to list all the reasons why. While I was cheering in silence and agreed with everything he said, and had more to add - I said nothing except "do what makes you happy".
And……they did not break up and "everything has changed and they are SOOOOO happy". Thank goodness I kept my mouth shut.
Have known people to see some "real" evidence of cheating, inform a partner, and then lose the friendship.
Its very bizarre to me how that works.