Married men who choose to have affairs are to blame for choosing to break their vows and have an affair. The OW is not to blame for his choice to do this. The MM has made a morally repugnant choice. He is doing something he knows will devastate people he knows and has made promises to. Everyone seems to agree with this point.
It seems to me, on reading it all here, that where posters stand with how they view OW/ being an OW hangs on whether or not they think that knowingly entering into any kind of relationship/ having an ONS with a married man/ man who is in an agreed, committed, monogamous relationship is a morally wrong/ repugnant thing to do.
Views seem to depend on whether or not you think it is wrong to do and conceal something that you know, if discovered, will devastate somebody else, including strangers.
Interestingly in a lot of posts from those who have been OW in the past, there is a common thread that with hindsight, they deeply regret what they did and don’t like that former version of themselves at all, but at the time when they were OW, they did not feel that way.
Most posts from current OW seem to show very little (if any) guilt about their relationship with the MM, or empathy with the wife. They don’t seem to think it’s morally wrong at all to be an OW, hence they are fine with their choices.
Unlike the MM, the OW possibly does not personally know the wife and children, has made no promises to them. So they are people to whom she has no obligations and they are strangers. Therefore they consider it unnecessary to consider them when choosing to continue the relationship and view them as the MM’s ‘problem’ and not theirs.
The MM and his family are in one box, when they are together, and the OW and the MM are in another when they are together. One world has nothing to do with the other so why feel guilty? It thus makes sense to them and it’s absolutely their right to have these viewpoints and beliefs.
I can only conclude then that if you can answer the question “Do I feel ok deliberately participating in something which, although I didn’t initiate it, I definitely know might cause terrible harm to others, including strangers?” with “Yes” , then you’ll be fine with being an OW.