If it were not an ethical, why wouldn't he have admitted to it the minute she asked if he had proof? Why would he and others here think he should try to avoid having it come to light that he did that? I think if it doesn't pass the sniff test, it's fishy.
But since you asked I thought a little more. There's an NPR episode about a cop whose commanding officers had illegal ticket quotas and punished those who didn't drum up enough tickets, who advocated arresting people who hadn't done anything, who reclassified cases to improve the city's crime statistics. This guy started wearing a tape recorder all the time. He had a hidden tape recorder running the day his colleagues broke into his home and forcibly placed him in psychiatric care. I did not feel he was doing wrong surreptitiously taping these blatant ethical violations so that he could possibly create change.
But a marriage is not so black and white. He had plenty to suspect, and his marriage was not thriving. He played along with moving OM's stuff and left them alone together on purpose to see what would happen, and hid his phone to tape them. Now he's willing to face his wife's ire by accusing her of an affair with OM, but not to face his wife's ire by stating how it is that he knows about it. I don't buy that it's to avoid her being mad at him. I think it's because he feels icky about having done it. And I believe when you have that icky feeling you lose a little self respect every time you try to hide what you did in hopes someone doesn't find out about it. I just believe in owning up, facing the music, admitting that I'm not the 100% good guy to your 100% bad guy.
I'll have to admit, he had good reason to suspect, and was right in his suspicion, and she's bald-faced lying to him, so I can see why he resorted to it. But I don't think he feels good about having done it; why not get it in the open and admit remorse.
Adinva 51, S20, S18 M24 total 6/15/11-12/1/12 From IDLY to H moving out 9/15/15-3/7/17 From negotiating SA to final D at age 50 5/8/17-now: New relationship with an old friend __ Happiness is a warm puppy.