I really think that this isn?t black and white.
I think that women often fall for the ?my wife doesn?t understand me? clichet because although it?s often just a clichet, sometimes it?s true, and so for all women they want it to be the one for whom it?s true, so they can be the one to save him from his unhappy marriage. And sometimes it?s true.
Mil has an aunt who was in a relationship with a married man for 40 years. She had a child by him, something which was deeply frowned on in those days, but she proceeded to raise her child as a single parent, with this man coming to see her once a week. But his wife was seriously unhinged. She had always told him that if he ever dared to leave her she would kill herself and his children, she told mil?s aunt this and she also told her children when they were old enough . So they carried on seeing each other in secret. She was definitely the other woman, he would go away with his family once a year and she had no idea where he was. If anything had ever happened to him she would never have known. When his wife died they did not move in together or anything like that, they?d become so used to living apart that that?s how it always stayed really. But they stayed together and a few years later he developed cancer and sadly died. But before he did he asked his children to look after her. They are all very close now, despite the resentment they obviously (and understandably) had for her when they were growing up. She could have had so much more out of her life. She could have moved on and possibly found happiness with someone else, but she truly and deeply loved this man, she is by no means a slapper.
Also a friend?s sil has had several affairs, but she has told her dh that if he ever leaves her he will never see his daughter again, and she is enough of a psycho that she would follow that one through. So if he happened to meet someone else would that make him cheating scum? I don?t think so.
Also, while I think that it?s a noble centiment to say ?leave one relationship before embarking on another? how realistic is that? If a man (or woman) falls in love with someone else and leaves their partner to be with that someone, will it hurt that partner any less being told that nothing had actually happened between them? Or should the one who is leaving make up some reason why he is leaving and then (per chance) meet someone new? oh, a year down the line? In which case they are still perpetuating a lie, so is the betrayal any less?
While I detest cheating of any kind, and would never want to put my dh through that, I do think that the ?all men are bastards/all ow?s are slappers? ideal is a little too simplistic.